Never seen that bottom conveyor leech before. I know Dean hops around on top, but I'm not sure if he gets as many points for it. I don't have much experience with that or any other point pressing because I think we're still a long way from needing to point-press D2K and the game is tedious enough as it is! It's fun to see people finding the spots to do it though.
The biggest gain comes on Level 2, where the timer speed and upper conveyor pie frequency are the most ideal. On Level 2 you can gain about 3,300 extra points from pressing than you would otherwise gain by "speed-running." I think it shakes out something like this:
Pie Pressing on Mixer:
Level 1: ~1,200 extra points possible
Level 2: ~3,300 extra points possible
Level 3: ~2,100 extra points possible
Level 4+: ~600 extra points possible