I played baseball through college. I played three sports in high school. I never tried to influence my kids towards baseball/softball. But it's what they play(ed) in college. They also played four sports into middle school and three in high school. My son was cut from basketball soph year for missing all the off season workouts and summer basketball. He played rec basketball the rest of high school.
My my kids never played baseball/softball out of season until high school. After 8th grade each played fall ball in addition to their fall sport. Winters were for physical training ing in addition to their wimter sport. In high school baseball/softball became year round.
Senior year my son fell and separated his shoulder doing an agility drill. It required surgery. The ortho (also has pro clients) said my son's shoulder had a lot of wear and tear. It wasn't from pitching. It was from all the contact playing sports. He's a very physical athlete. He's a very athletic kid who plays like a grinder. Putting his shoulder back together had him throwing harder.
So it's not necessarily pitching too much, too little, playing one sport or playing multiple sports. All an athlete can do is take care of his body the best he can and hope for the best. As far as throwing and pitching I do believe kids pitch too much and throw too little. My son threw almost every day during the season starting with LL.
i also believe just because a person is/was a pro athlete doesn't mean he knows anything about youth sports and youth's bodies.