One other take on Ronnie's speed. The pause at the back is where I am doing the final fine tuning to the planned strike to the white. So I hypothesize that; Ronnie's longer pause at the back comes on the shots requiring special sauce on the cue ball. Or even just super fine precision on the strike to the white. The movement of his cue ball small distance and into small spaces is often obtained knocking the back off the pocket.