As I see it, the difference between the two is this. The dry throw, where you go through the moves without the ball, can be useful when you’re learning a new pitch—to a point. I much prefer the second one, where you get up on a mound, whether in the bullpen or on the playing field, and throw the ball; you get the feel of the pitch, which is absent in the first go-through-the-motions throw. I remember when I was talking to Eddie Lopat, and I mentioned that I was using the crossfire a lot. He said, “Let’s see what you’re doing with it—just go through the move.” I did so, and immediately he called my attention to the fact that I wasn’t getting as much momentum from the stretch as I was from the full windup. This was a case where the “dry throw” was useful; it pinpointed a mechanical problem. Needless to say, we fixed it in short order.
From what you’re saying I’m believe that you’re saying that dry reps can have more benefit to lower body or general body movement mechanics and not much benefit to specific pitches or arm action in particular.
That’s where I believe dry reps can have their benefit. They let your grow through your motion and focus on specific things like momentum and not have to worry about throwing.