The joint motion is reverse dart wrist motion. Flat arm position, just the hand going back and forth. When you see this, and there is no obvious “evens” patterning in the vocabulary, it’s usually just trapped motion or an escape that’s not being used.
It probably doesn’t matter. George never played pick-all-the-notes vocabulary in any systematic way. Occasional examples like the “In My Dreams” lick I think are mostly spray-and-pray one offs. The picking was just for a little spicy flavor, not the main dish.
I love George’s playing of course. Among the most original players from that era with instantly recognizable tone and articulation.