I believe it was more the physical early bloomers than pitchers or hitters. In our USSSA region there was a particular pitcher and particular hitter that stood out over all the rest. The pitcher was hitting low 80’s with command relative to 13u. The hitter hit a ball off my team that must still in in orbit thirteen years later. I think Direct TV rents space on it for transmission.
Both kids were physically developed 13yos. Neither kid grew beyond 5’9”. They had better than average high school baseball careers.
Not all early physically early bloomers are flameouts. I know a kid who was a competent 15u pitcher at thirteen. He became a 6’5” ACC pitcher throwing mid 90’s. If people remember Robert Stock he was hitting 90 at fourteen.