That is not my experience at all. Most of the kids that I saw that were the top players in AAU at 12 ended up being the best in HS. For instance.
12 AAU
Justin Jackson - TC Roberson HS Drafted
Chris Luck - South Granville HS Drafted
Madison Bumgardner - South Caldwell HS Drafted
Sam Runion - AC Reynolds HS Drafted
Ryan Leach - East Rutherford HS - UNC
Zeke Blanton - East Rutherford HS - UNC
Justin Poovey - South Caldwell HS - Florida
Jason Wallace - Ragsdale HS - App State
Catlin Carter - Ragsdale HS - App State
Wes McBride - West Forsyth HS - UNC Greensboro
Patrick Johnson - St Stephens HS - UNC
Vance Williams - Athens Drive HS - NC State
Quincy Lattamore - Middle Creek HS - Drafted
David Mailman - Providence HS - Drafted
I could on and on. All these guys were top level 12 year old players that I personally saw play. The same could be said for the 08 class.
Cameron Conner - South Wake Storm AAU - NC State
Pratt Maynard - Durham Diamonds AAU - NC State
Jeff May - Durham Diamonds AAU - UNC
Sean Madden - Durham Diamonds AAU - Lenoir Rhyne
Mike Dimmock - Triad Thunder AAU - Wake Forest
Mac Williamson - Wake Thunder AAU - Wake Forest
Jeremy Dowdy - Wake Thunder AAU - Clemson
Cameron Cockman - Triad Thunder AAU - UNCW
Tyler Hanover - Kernersville Cardinals AAU - LSU
Again I could go on and on as well. Most of the kids at 12 that were very good remained the top players in HS. Were there some that did not get better? Yes. But my experience has been that the better players at 12 were the better players at 13 and 14 and so on. Are there guys that develop later on , yes.
It is not definite that they will continue to be the better players. But from my experience it is a good indication of things to come.