The growth spurt may exhaust him. He may have to grow into his body. He may not yet be strong enough to propel this newly enlarged vessel. His body may betray him. Swimmers' interests change.
Swimmers get tired.
Pursuing swimming excellence requires walking the fine line between pushing the limits and overtraining. Sometimes your swimmer will cross the line. Sometimes the learning curve is steep. In this competitive sport, your child will constantly be compared to others in a constantly changing competitive environment. It will neither seem fair nor understandable.