Doughnutman,
I believe your “theory” has lots of merit to it, but one must be careful when describing what a player’s “natural arm motion and delivery” or “natural arm slot” is. Most kids throw with something close to what’s “natural” for them, until that 1st coach, dad or not, gets their hands on them. As soon as that happens, the “natural” things they did will have been modified, and then the theories all go out the window because its no longer possible to see what was “natural”.
Here’s something else that a lot of people don’t even consider. People used to get all bent out of shape and wanted my kid to change his slot from low three quarters to something higher, both as a fielder and a pitcher. But every time that happened, he’d experience arm and back problems, so I always told him to just go back to what worked.
What we eventually found out was, he had slight scoliosis which accounted for the back problems. When he “bent” over sideways which made his slot lower, his back didn’t hurt. But trying to throw like most kids are able, it caused back problems.
What we also found out he had a Type III acromion processes. Here’s a bit on it, http://www.aafp.org/afp/1998/0215/p667.html but you can check into it for yourself. What happened was, when he moved his arm slot higher, he was unknowingly creating an impingement and creating his own shoulder problems.
Of course we’ll never know what ultimately caused the problems, but those two things were definitely major contributors, and they are things that very seldom are considered by coaches or anyone else.