Didn't watch the whole thing but heard / saw a lotta good stuff in the parts I did watch. I would stress delaying the shoulder adduction he speaks of. You want to keep some stretch in the pec muscle for a while. Stretch (stored or PE) and then release (KE) at the appropriate time.
I see many with the elbow too forward at the trophy or the pec stretch released too early.
A lot to digest wow! I have always wondered about ulnar wrist deviation on flat serve vs kick serve. Apparently there’s more ulnar deviation on flat serves. Great video thanks for posting. I’m going to watch it again when I’m more alert.