Holdbacks deprive those kids of appropriate age of spots at the higher levels.
Exactly the opposite of growing the game, holdbacks are effectively shrinking the pool of players.
While this may true nothing is going happen till the college coaches get on board. You don't know how many times a college coach encouraged a player to repeat or declare a PG year. Happens all the time.
If the people who will end up being their coaches are telling them to do it, what are they supposed to do?
Both of these posts are absolutely correct. Public school parents of very good players (not the 'great' player) have a bit of a dilemma if their son ever has hopes of playing at a D1. Just looking at D1 rosters filled with prep school players is all you need to know. (There are a few exceptions of course)