It's like the FD thing, educated conjecture on the surface, but certainly ringing true in the context of what goes on in crewed aircraft when the PNF's confidence level is impacted.
When I flew as an instructor during type rating training in the aircraft, it was also my job to provide all the necessary support to the trainee that he could expect to receive from a dedicated, disciplined first officer.
As the instructor, however, I was a terrible co-pilot when I could see a potential compromise of aircraft control.