I would have to completely concur with your theory, and think I holds a lot of weight (pun intended).
To me, remaining within the same pediatric growth percentiles makes sense for the same reason. And I also do think there are probably a LARGE amount of people who are not at their set points and perhaps think they’re “destined” to be at that weight, for the reasons you mentioned.
It’s pretty morbid but traditionally speaking, there has to be some validity to the body structure/weight correlation.. Otherwise, why would forensic pathologists bother?
I think if people had a good idea as to where they were likely to end up after metabolic restoration, the whole process would be easier.