Good practice using two hands.... Both off or both on! Guess its why 380/350 only has one button for both FDs.
Now I don't fly an Airbus, and I understand the both on/off principle, but why did Airbus decide to do that?
If the PF decides to hand fly (no AP, A/T), wouldn't it be wise for the PM's FD to be up so he could more effectively monitor the PF's performance?