You might be right about the change of the basic picking motion from wrist to forearm. I had also noticed that JP “attacks” the strings in a rather brutal way when he plays faster stuff.
Thanks for the video, I had never noticed that kind of change in the thumb position.
I noticed that I am actually struggling with picking on ONE string when I play the high e string and the b string, so I tried looking for videos that demonstrate how a string and the pick “interact”, and I found two that are helpful (see below). Which brings me to the question: is there content by CTC that actually shows how you pick a string in detail? I know this sounds crazy, but I have been focusing so hard on the string changes that I never really became aware of what it takes to play on ONE string.