Most full-rollers do have hand movement, that's why they're full rollers :-)
I was a full-roller when I first started, so have some experience with it. It took me a year to get my track off the thumb-hole. I still have a 6 plus inch PAP and a down adjustment :-) I got off the thumb, but not much :-) I discourage any delivery where the thumb get's to the 9 o'clock position.
When I watched the videos, his position at the bottom on the way back causes way too much physical adjustment to overcome in his last 2 steps. More body angle would alleviate that and free up the arm swing.
To me, the simplest way is to let the ball drop into the empty area vacated by the second step. The ball comes back slightly inside and goes back forward slightly outside.
That slight inside out delivery really frees up the arm, the release and puts the body at the right angles to offset all weight shifts with the trailing leg.
It also allows the bowler to work the inside of the ball. For a full-roller, that may not be needed.
That's just my opinion, I could be wrong. -- Dennis Miller