Dont know his exact situation at all, but i sympathize because i am older for my grade and i was never held back. It was all based on my state's birth date requirements for starting kindergarten.
It will serve him well in college. Probably is not tapped out training wise in high school because of extra physical maturity. In my opinion more likely to have major collegiate success.
In college and beyond you have to compete against older people. Age nearly becomes irrelevant after high school. Ive had competitors and teammates in college who were literally 27+ years old. These people are way more deserving of criticism, or at least age transparency than Maton is.
There is no age group qualifying for the olympics. If a 20 year old gets 5th at the trials it doesnt mean he actually deserves to go. Good luck in the future Maton, where being older, but not outrageously older than your class, is going to help a lot!