I think Airbus are trying to keep both pilots in the flying part of the loop. Which is laudable enough. But if I am flying manually and setting off drift to track a course, it is a right pain for both of us if I keep saying Heading left 3° Heading right 2° etc, just to centre the heading bug. Much easier for PF to click the HDG knob as required.
I would like to think that PM is always watching the PFD, ND and N1/EPR even when talking to ATC or the cabin. I certainly do when I am PM.
When PM has been head down in the MCDU, they should look carefully to see what I might have changed, (I do if I am PM), and I will tell them anything significant as well.
But, I don't write the SOPs