As I see it, there are at least two styles of pitching--those who pull the ball down the back side and those who do not. Generally, I see the pullers as being the "IR style" pitchers, and the pushers as being, what I call, the "hello-elbow style" pitcher.
Again, while "hello elbow" is a term to describe a follow-through, I think it's generally associated with the pushers.
While "internal rotation" is a term used to describe arm motion, I think it's generally associated with the pullers.
To me, this is a pretty good understanding of high level mechanics.