Here is a substantial argument for you cheater_1 and any of those that considered your points accurate. I am not flaming you, as you present a great argument, but it is very misleading.
IF POSSIBLE, before you read my post, take about 20 minutes to read / scan this article, as it is the BACKBONE to my argument, supplemented by common sense.
Research done by the AMERICAN PSYCHOLOGICAL ASSOCIATION.
I at first thought chess was related to IQ levels; that if you had an average IQ then you could never go far. Likewise, you consider photographic memory the KEY trait, REQUIRED. This is FALSE.
All of these players that you speak of have done something that you probably have NOT done, or if you HAVE done it, you have not done it for as long a time. It is called deliberate practice.
Let's consider the boy who you spoke of, the one who reached 2500 before he reached 13 and then gave up. There is an EXPLANATION for this other than the fact that they gave up because they go, "I don't have a photographic memory, I can't do it." Cite that, and quote him. That assumption is completely misleading.
The reason he gave up, and I use this research as my proof, you need to read that article; The reason he gave up is because, as you said, he engulfed his entire young life into DELIBERATELY PRACTICING CHESS. This, according to the research, leads to BURNOUT. When you undergo burnout, it is rare to recover, you simply lose interest. Had the boy not have gone so obsessively into it he would have achieved his mark of 2700.
You see, deliberate practice is NOT easy, because it is NOT nearly as fun as playing the game. Puzzles / reading books / completing tactics / analyzing games of the master - it is WORK. Football players must workout in the gym and go to practice countless times to reach greatness. The same to all athletics. Athletes become great in this exact same manner; physical stature has NOTHING to do with it. The reason there are few 5"5 wide receivers is because they are NOT motivated, because they do not have the confidence. Motivation and Deliberate Practice for 10,000+ hours = Greatness (article).
Now, as you may question, "why do we see more teenagers go so far as compared to those who start late." Studies indicate that the later you start, after teenage years, then the more your maximal level decreases (article).
Several CONSTRAINTS - and I mean there are LOADS of constraints, NONE of which are related to PHYSICAL or MENTAL stature - several Constraints inhibit or block progress.
A) Motivational - as with the kid, burnout. Also, if you start at such a young age, you MUST have parental support. They have to fund you, give you a teacher, etc.
B) People tend to PLAY the game more than they deliberately practice it.
C) All chess masters, and I mean ALL, including those you mentioned (this article as my source), all of these chess masters who have obtained the 2700 rating: They have put in over 10,000 hours of DELIBERATE PRACTICE alone. You cannot tell me that you have done that. In your other posts, you say you spent the past decade PLAYING, not practicing.
So the main idea here is that if you have:
Dedication not only to the game but to practicing it for thousands of hours over at least 10 years of your life, then you will go the distance. This applies to the greatest football players, hockey players, etc. The reason there aren't the MILLIONS you mention is not because they don't have photographic memory; it is simply because there are very few people who have all of the ingredients to be able to practice and keep themselves motivated for 10,000 hours.
I believe that's a pretty substantive argument, my cheating friend.