Just a little background on my son. He didn't pitch a lot. He was a hard thrower but not to accurate. He only pitched once a month or less except in LL. He then pitched once a week as a freshman on JV. Most of the time he played on teams that had lots of pitchers and they always wanted him in the field for his d. Did we do everything correctly? No. Nobody does. But he threw vey few innings and never expierenced pain until his sophomore year after they started messing with his throwing. He was always a little under 3/4 from the field and the mound. Big push from the mound. They made him throw much more overhand from the field and mound and stopped him from pushing so hard from the mound. Then the pain started and ended with Labrum surgery after a bullpen about a year and a half later. He always took off at least 2 months every year and usually three.
We tried to do everything correctly but nothing ever hurt until the HS coach changed things.
Who knows why it tore? Maybe just because it was going to anyway, you never know.
Maybe the question should be when did you first start to notice pain when throwing? I would love to hear from players who went on to have surgery when they first noticed discomfort in their arm.