The Rotor puts tension on the balls and stops when a certain level is reached.
I assumed the Z2 did something similar, but I'm not sure. Lets not get into the discussion of "true" force feeding. If a loader like the Z2 can react quick enough to a gun firing that it doesn't need to constantly put pressure on the paint, all the better. That will mean you won't get oblong balls just from sitting in your feedneck on hot days.