I did not notice that
I suspect you can see the forearm muscles pronate as a result of the tighter grip as well. That's how we pick CU traditionally.
I took a class on pitch picking at the WCWS this last year w Gayle Blevins and John Tschida. It was eye opening. Every game in the last 2 days was decided by picking pitches and reacting to them. Especially by Tim Walton IMHO.