There are very few clear cut 15 year old athletes who are no brainer future draftable players. Maybe maybe 1% of the small percent who make the nfl/mlb/nba. Maybe.They don't exist in your world?
My opinion on it is not just based on biology. Young teens should be focusing on things other than bodybuilding, IMO. All around athleticism is a great thing for anyone, but focusing on maxed physiques is not a psychologically good thing for teens, IMO.
P5 level scholarship at 15 is certainly higher but still very very low.