"I have said it a few times before whether the AP is on or off pilot's scan or monitoring does not change. "
Should not change, I totally agree, but in some cases we have seen that it does change.
How could we avoid this? Well, perhaps if flight directors were able to be switched off most of the time, then all our scans and recall of correct attitudes would improve, because instead of glancing at a square box over two crossed lines, we would become used to looking at the raw PFD and assimilating and mentally cross-checking any attitude change with what was commanded and intended.
We would have to look at the raw data, even to monitor the automatics, and our knowledge of correct attitudes would become ingrained.
The human brain will always do the easiest thing and it will not maintain something it rarely uses.