Skylark,
If your point is that pitching at a young age (8-12?) is not inherently more injurious than at older ages, I don’t know of any medical literature that supports or refutes that opinion. However, the logical conclusion about starting at a young age is that the child will throw more pitches over the span of his pre-adult years, which will typically contribute to overuse. In an ideal situation, where the parent understands and successfully manages all of the risk factors (and I actually know someone currently doing this with his 10 year old), I do believe that a child can begin pitching at a young age with very little risk of injury. However, I’m afraid that scenario is extremely rare, and that isn’t going to work for the masses.
I was unacquainted with competitive baseball when my 2015 started playing t-ball. I have a laundry list of things I would have done differently. Ironically, he probably would have played even more baseball had I known what I was doing. I agree with you about overuse, and I’m convinced that (along with inadequate recovery time) was the primary factor in my son’s elbow issues. Flawed mechanics and conditioning played a part, but I think we could have avoided his injury if he simply threw less. Others might reason that proper training would have corrected the problem, but I just don’t find that to be a realistic option for the sport in general because of the expertise and level of commitment required.
Also, I can’t sight a study but my experience tells me that the damage from overuse varies greatly from child to child (back to your college pitchers). I would go as far as to say that even the LL pitch count limits are too lax for some kids. I would love to see some kind of baseline valgus stress test in the future, with regular follow-up testing. Anything that would give parents some object feedback about their child's arm health.