THAT SAID, I have an in-universe explanation. If a griffin is raising a finger, it's probably because something comical is afoot. It could put them off-balance, and it doesn't really make any sense given the configuration of their feet.
Meanwhile, a raised finger (toe?) is a bit of an odd gesture for them to make. It's a thing they can reasonably and naturally do as a form of expression, and it's not always convenient to swing wings around just to express something. This page also has what I consider an odd mix of griffin gestures. I wanted to actually have it on this page so we could see what exactly Liam told Dwight, and Dwight's reaction to it. If Liam's explanation needs to be said again, it will be via 'and so it was explained again' narration.
