That's what I've been saying for weeks. No sound ball-striker hits a shot, and thinks to themselves, "I will now supinate", during their stroke. It's a consequence of other things happening early in the stroke. That's why all these threads about how max supination and pronation and every other buzzword are the key to understanding the modern game are so counterproductive. When you're teaching someone to pronate on a serve, you don't even have to use the word pronation. You can have them throw a football and then mimic the release where the forearm and hand turn over. The guys that really pronate on serves aren't thinking at contact, ok time to pronate. It happens so dramatically because they have great fundamentals, like their shoulder turn and uncoiling which build the racket speed.