If the Autoprop can spin the shaft when it is in reverse, that would be a bad thing. If it never spins when in forward, then that would be the correct position, for sure.
Anytime a prop back drives the shaft with the transmission in gear (F or R) it is wearing the clutches.
For a Maxprop the correct sequence is to stop the engine always in forward, then shift to reverse to be sure the shaft does not spin. If stopped while turning in reverse, the blades do not feather. Under normal conditions, if the prop is fully feathered, it will not spin in neutral either.
Annapolis, MD, USA