One thing I would like to add to this discussion concerns "bona fides" and whether a pitching "guru" has them or not. Personally, I was taught to pitch by my father, who was a pitcher himself in his own right. I pitched through high school in a large city and that was the end of that (foolishly I tried walking on at a major D1 and was promptly tossed aside). Many years later I started to carefully study pitching when my son started to play baseball and asked me to teach him how to pitch. I have since learned so much more about pitching than I ever knew. I have also learned that pitching "gurus" who have college or professional pitching experience can at times give bad advice.
Just this past season, a "former college pitcher" serving as an assistant coach on my son's 14U team came to me because he wanted to change my son's (very common) footwork, which was taught to my son by a former pro pitcher and used by Greg Maddux and many other MLB pitchers today. At the time my son was pitching lights out, and this ass of a coach couldn't give me a reason for making the change other than on his college team some years back "It's not what we did". Huh? Of course I told him "No. Check out videos of Maddux".
On the other side of the coin is a local pitching instructor who never played baseball in his life (he won a state basketball championship in high school). This guy instructed and coached his pitcher son from a very young age. The kid went D1 and was just drafted by MLB. Trust me, this local pitching instructor with a basketball background is an insufferable egomaniac who never let anyone beside himself instruct his son when it came to pitching. And yet the kid is now in the pros!
So basically, yeah, it's neat if your pitching coach played college or pro ball. The downside is that their advice is not always good. Playing at the highest levels does not always translate to knowledge or ability to teach. And, when their advice is not good, it is harder to reject because, well, "He played pro ball!" So the fact that O'Leary played baseball all the way through Little League () means little to me. I am more interested in whether his theories hold water. I understanding some MLB teams and players have actually consulted him, so it appears at least some think his theories are worth a look.