I have never seen this mentioned anywhere, apart from that site that's now gone.

I'd probably need some more details about exactly what this theory was saying before being able to comment on it...assuming there are any more details to it other than what you've said.

Addressing your other points...

looking back to all the manifestations I have had in my own life, I have never had the thing or the situation turn out exactly as I had imagined. Not once. I have had the kind of car or house I had wanted but they were never exactly how I had imagined them.

If you were going to your local supermarket armed with your shopping list, would you buy the first item off the list, go home, mark that item done from your list, and then go back to the supermarket again to buy the second item, go home, mark that item done from the list, then go back again to buy the next one...and so on?

Or would you buy them all at once since you're already at the supermarket?

It makes logical sense to buy everything in one go while you're in there, doesn't it?

I guess that's why the shopping trolley was invented :)

The Universe (Law of Attraction) operates in a similar way.

You never have just one desire, wait for the Universe to manifest it, and then have another desire, wait for the Universe to manifest it, then have yet another desire, wait for the Universe manifest it...and so on.

Instead, you are launching desires all day long (without you doing anything other than being alive) and, like buying multiple things from a supermarket, the Universe just manifests them all in a blended buy-it-all-at-once way. (More about blended manifestations here).

Because your manifestations are blended, you often don't recognize them as yours - but they really are.

you'll NEVER get exactly those situations that you have been imagining

The thing to remember is that the Universe doesn't speak the English language, or any other language. Talk to it verbally all day long and it won't understand a single word :)

And, contrary to what some would have you believe, it doesn't even understand (or respond to) the pictures/visualizations/imaginings you hold in your mind.

Instead, the Universe (Law of Attraction) understands and responds to...Vibration.

Our emotions are indicators of Vibration.

So it follows that, from our physical standpoint, our Universal Responses (manifestations) are linked to what we're experiencing emotionally

So to understand what you're getting physically and why you are getting it, you have to understand the emotional component of it.

Saying "I want this" and writing out a verbal list of things you want is very unlikely to get you precisely what you want.

But writing out a list of "I want to Feel this" will get you precise matches every single time, expressed through different and diverse physical manifestations...because those things you want to feel are expressed in the vibrational language that the Universe can understand.

Hope that's clear.

Nice observation.

Only logical explanation that I see would be that when you place you attention on something you are actually saying "I want this". When you are wanting something that means you don't have it. Because if you did have it you wouldn't want it, you wouldn't need it. So when you are wanting something(placing your attention on something) that's exactly what you are given back - more wanting. With wanting you are acknowledging the lack of the wanted thing and so perpetuating the not having of it as long as you continue to want it.

So that would be the reason for it not materialising

See my question What is wanting for

An amazing post.

i think that is because we do not controll the events. its the univers's/god's gob. and while trying to controll the events we dont live in the now. we dont let go and let things just happen for us. it is as if we're ruining our own surprise.

EDIT:

i just watched a video about power of thoughts(i dont share it cause its a rabi speak in hebrew ) and he said that we cant see all times (future, past and present) because if we could see all polibilities we would be lack of the right to choose. and thats the reson of why we live in a space-time reality, so we will have the ability to be free and choose. if we could see everything we'd know how to act and if what we do is right or wrong in advance. and thats sounds powerful but its taking from us our freedom because everything already known.
so i guess knowing all posibilities leeds to confusion and boredom .

I had an experience yesterday that resembles this thread.

In my past, there were two separate incidents of one-of-a-kind objects that I came very close to getting/having, but both slipped through my fingers. These two items have haunted me, they were "perfect" for me, and I would periodically think of these two items and feel the pang of not having had the chance to have those objects as my own. And that they will never come around again. 

A few months ago, I consciously realized the limiting and negative thoughts I had about these two objects. So I started working on soothing these thoughts, which I do by feeling fully the negativity, until it's energy runs out. I wasn't even really aware of the progress I was making, because i wasn't doing it to get anything, but just to feel better.  I was challenging my belief that rare items, are, well, rare. Challenging my assumptions about the whole idea of rare and forever-missed opportunities. Just because to think like I did...didn't feel good.

Yesterday I went to an antique shop that I love and went to my favorite dealer's booth. I had just been there a week prior, but today, there was a gorgeous tufted champagne velvet sofa, from the 1960s, in mint condition, perfect for my 1960s home that I have. And I just stared at it, because I suddenly remembered an incident 10 years prior. 

I was on vacation in another city, and saw, for the first time in my life, a vintage champagne tufted velvet  sofa. It was so glamorous, in a James Bond way, and I felt a genuine anger and sadness that I had to leave it behind, because I was traveling and had no way to bring a sofa back to my then-home 1500 miles away.

However, I completely forgot about the sofa. Over the ten years, I moved several times, got different sofas for each house...but this house that I have now....the room for which I needed a sofa is very retro, with the original silver foil geometric cube wallpaper, and no modern sofas worked to this aesthetic. 

So here, right in front of me,  is that champagne velvet sofa I saw 10 years ago...except even better. This one is about two feet longer, and it had a sexy curve to the front of it. IOW, it was perfect for the space I have for it. 

I was telling the cashier at the antique shop this narrative about seeing a similar sofa 10 years ago, and how it's so true that the universe never forgets a genuine desire, but it waits for you to align with it. And they said "Yes, you had to change, and go through things, so you could change, before it was ready to come to you again." How nice to hear that out in the wild! 

I've been looking for the perfect sofa for this home for almost two years. I didn't even know what I was looking for. And it wasn't until I started releasing my negative thoughts about ~ "Things I love and desire that are rare don't show up more than once in a lifetime", that this sofa showed up.

I explicitly see why the other two objects haven't shown up....that I still have their loss in my vibration, because i still think of them in a vibrational way of "I don't have them and I missed out on them." This sofa, I didn't even remember, I never thought about it. But I was so in love with it when I first knew it existed... it's perfect for my personality and style...and the universe waited till I had the perfect house for it, and till I released some of my limiting feelings about rare objects and scarcity. And brought the sofa to me but even better than before. 

The funny thing is...how I felt, when I saw the sofa...it was another deep thud of enlightenment, a deepening/confirmation of what I already knew.  I saw it and just thought "Oh, of course!" 

I'm sharing this because I myself prefer reading anecdotes/real life experience narratives over the abstraction, so this if for anyone else who likes anecdotes too. I love it when I consciously recognize the Law in action in a positive way!