Here's an example of a kid I knew had peaked early. It was a LL districts. We show up at the host park. I was told of a kid from the host park who was hitting balls to the rooftops across the street. The street ran behind right field. My response, "A lefty!"
When I was told he was a righty my first thought was, "a big, strong early bloomer who swings like a rusty gate." I was right. At age twelve his father was referring to him as "The ticket to Williamsport." The team didn't get out of pool play.
The kid did manage to win both his games pitching. But he was a non performer at the plate. The first opponents threw him nothing but changes and curves. The next three teams did the same. If the kid had a tutu he could have joined the circus as a dancing bear.
The kid hit nothing but high flies in middle school. Mid way through 7th grade he wasn't a position player anymore. He never made high school varsity as a pitcher. He was 5'8" throwing 75 in LL. He was 5'9" throwing 78 soph year of high school.
The dad was 5'4". The mother probably wasn't five feet. When the kid was in LL his dad thought he had a future MLBer on his hands. I thought the kid would be a serviceable pitcher in 13u. I backed off when the dad asked me if pro scouts would be at the games. I was also told the dad knows nothing about baseball yet called pitches from the stands.
A kid I knew (played for an opponent) was a man child in 13u. He owned the game. He was still a stud in 14u. But you could see other kids were catching up. The kid didn't make his high school team. He would have been a serviceable high school player. Grades and pot held him back. He was another case of a big 13u player with small parents who was about done growing.
When my son was in LL the 12yo team went a long way. Only four kids played high school ball. It was a team full of very athletic kids who could out muscle and/or out run the small field. They all became high school athletes. They just weren't baseball players. The team that beat them in states was led by a stud who didn't play high school ball. He was a big kid who peaked early. I think every other kid on his team play(ed) college baseball except for the 4'11" kid who became a 6'4" college shooting guard.