high school due to privrledge, but had exhausted their potential before getting to college - no upside left.
All of that priveledge provides a temporary advantage, but by the time they are in college other players catch up on tehnique, and have more athletic upside that starts to show when the knowledge and training gap is closed.
Same thing with parents holding kids back a year for athletic reasons. Big advantage early on being a year or more older, but that evens out by college age and suddenly they are pretty ordinary.