Let him play where he can or has the most fun. If that's utility, so be it. HS Coaches usually stick kids where they are best or need help. Enjoy the game, learn to train, get stronger and be a better player at whatever position he enjoys. My kid found out the hard way that bigger kids usually play ahead of smaller players. Our HS Coach believed in seniority over talent. It helped my son grow into a pitcher and that role carried him to where he is today. Enjoy it as a parent, it goes by before you know it.
How is that ole undersized max-effort thrower doing these days? Still mowing ‘em down with mid 90s stuff?