My son ( 15 year old freshman) started saying the same thing. Had a bad showing at a tryout, and one of the coaches told him he wasn't very good behind the plate. He told one of his pitching coaches, that he only wanted to be a P.O., but that coach said "don't give up hitting yet. Plenty of time for that later". Fast Forward (approx 3 months later); He's at the plate, with two outs and bases loaded, he hits a game winning double to the fence, to clear the bases. Then, Three weeks ago he hit his first "Dinger" , against a Mid 80's pitcher. He no longer talks about P.O.
Batting can be so frustrating ! Especially when success is only about a third of the time. I can see why kids get turned off. But, when the hits come, its a whole different feeling. I suspect it may be the same for your son. Of course, I'm only guessing. Best of luck , and whatever happens-keep the game fun.