Great points and video, I think the big reason people teach to turn your hand away from yourself during separation is that for some reason girls struggle to learn how to snap their wrists when they throw. When the ball starts facing away, your forced to engage the wrist to snap the ball, if the ball never faces away its more of a "pushing" action. They get separation and then straight arm it or launch it like a catapult instead of actually getting the wrist action of snapping like you said getting that "whip" result. I agree with transferring with your fingers on the top of the ball, I think there's a few ways people teach this but it's like hitting, you see all these mlb players doing weird motions and quirks in their swing but all of them eventually get to the same point in their stance where their locked and loaded to get on plane. For throwing, especially with girls, emphasizing getting that rotation and spin on the ball can help them focus on getting that whip and snapping feeling that doesn't seem to come as natural as it does to boys.
I should have been clearer when I mentioned "whip". I was referring to the whip in the elbow, not the wrist. Personally, I don't consciously think of whipping my wrist. In the Trosky video, he talks about catapulting from 1:30-1:35 in the video.