Should the back knee leg when the front foot gets down?

I was at the Phillies game and I was watching Adam Eaton pitch. I looked closely at his mechanics. He has a nice, compact, fluid delivery. I noticed as soon as his front foot touched he ground his back leg/knee turned inwards. It gave the impression of him almost jumping or twitching.

Also a question about his leg lift, it crosses over his plant leg then goes right towards the plate. Does that help load the front hip or anything like that?

He got rocked that game because he put it right down the middle and Randy Johnson even got a double, but his mechs looked pretty good ahaha.