If it's you, then the PM will have to answer and this is now several seconds during which the PF capacity to modify the FCU is severely impaired, since he's forbidden from doing it himself.
Why do you have to wait for the PM to set the FCU? If ATC gives you a vector, can’t you execute it while waiting for the PM to catch up? Why not just turn off the FD?
But obviously, asking the PM "two degrees left, no one degree right, etc.." would be too much time consuming (whereas adjusting heading bug alone in a single pilot operation is just the normal way of doing things and very easy), so you end up asking "set runway heading" and visualise a drift on the PFD
Another great time to just turn the FD off, as it increases workload.
I'm just questionning whether it's really justified, and wondering how it is the other side of the Atlantic at Boeing's.
I don’t fly a Boeing, but I’m on the other side of the Atlantic. First of all, there’s a lot less chatter in the cockpit. Previous company read FMA’s. The other companies here don’t. The only FCU change that is spoken out loud here in the US is altitude. I don’t know of any company that reads out headings and speeds. In the same vein, I don’t know if any US company that says “check” or “checked” to every change. I’ve seen some videos on YouTube of European cockpits that are simply ridiculous. Everything’s “checked”.
Now I’ve learned that here, we’re probably more relaxed because language barriers aren’t really an issue. It seems your airline wants you to do a lot of talking to coordinate FCU changes. My simple solution would be to turn off the FD when flying manually.