There is a boy who my son has played ball with since he was 7 yo. He started throwing a curve ball when he was 10yo and was taught the correct way to throw it. But most important he never threw more than 75 pitches in a game and wasnt used every other game unless there were more than 4 days between games. Maybe we were lucky and had three or four quality pitchers during our travel existance, but that kid is still throwing the same nasty stuff as when he was 10 and has NEVER had arm troubles.
Now on my sons HS team there were more hurt arms then i have ever seen, but by some parents admission it was strictly overuse and two were not curveball pitchers.
Its not the curveball that hurts arms, its overuse and improper mechanics, taught by overzealous coaches who just want to win at all costs.