First, let me say that I’m not a big fan of the idea that people should pass through the traditional High Cocked position. I just know that a lot of people are coached that they should pass through it. For the record, I would prefer that the elbow be extended more like 135 degrees (ball roughly at ear level) rather than the traditional 90 degrees.
Second, I think in general focusing on Scapular Loading is probably wasted effort, at least at first. Given the relative size of the muscles involved, I think a pitcher’s time is much better spent focusing on getting the rotation of the hips leading the rotation of the shoulders by the largest amount possible (anywhere between 45 and 90 degrees).
If a pitcher does have very good hip action, then they might indeed be able to pick up a few more MPH by scapular loading. However, I view this as a risky proposition for a couple of reasons. First, by trying to do something with the scapula, you could interfere with its normal functioning and increase the risk of injury. Second, it seems to me that, if scapular loading is indeed something that pitchers do (as opposed to something that just happens naturally) there seems to be a right way and a wrong way to do it.
I would describe the right way to do it as more of a right-side-up W; with the elbows at or below the level of the shoulders. I would describe the wrong way to do it as an upside-down W with the elbows above the level of the shoulders. I believe having the elbows above the shoulders increases the risk of rotator cuff problems.
My bottom line?
Spend your time focusing on the rotation of of the hips, torso, and shoulders, with the rotation of the hips leading the rotation of the shoulders. If scapular loading happens, just make sure it happens the right way (with the elbows below the shoulders).