You're right, of course.Van Aert would almost certainly have to drop muscle mass and then you never know what power output remains.
But even when we seem to have him figured out, he still finds ways to amaze (like taking the fight to Alaphilippe on his own sort of terrain yesterday i.e. very impressive).
I just don't find a lot of names on the "future star" list to be anywhere near as incredible (or constantly improving like WvA seems to be). Obviously GT cycling is different to what WvA excels at, but...
I've seen strange things happen in cycling before.