Of course I feel like an idiot when I disagree with Donley & Flisk, but I can't help it.
Here's Joe Nathan's pitching mechanics. He is out with a torn UCL. He is one of those "push off the rubber" guys. How can this NOT drag the elbow behind the hips? The problem starts right in the stance phase, look for yourself. The pelvis is already translating forward, and his arm hasn't moved from his side. Now why the elbow & not the GH joint? Look at his belt line in the acceleration phase. Pelvis is tilted posterior in the frontal plane (backward). He MUST drop the elbow to keep from "dunking the clown" sort of speak.
I actually called Flisk on the phone about this, he never called me back. I asked Phil Donley in person & he doesn't have a problem with this as long as the pitcher's body is anatomically sound.
But...how do you stop a runaway train?