A good briefing will include typical weasel words such as “ On this flight I expect you to conduct it as if you are in command on a single pilot operation. That requires you to do everything; to aviate, navigate, communicate. However, I may request certain clearances directly from ATC if necessary for clarity of intent, and will ensure that you understand any instructions received as a result.
Any emergency that is not real will be preceded by the words “simulated…eg simulated engine failure”. If a real emergency should arise, I expect you to deal with it if you are able. If you are not, I will take control with the words “my control”. Etc.
The confusion that some PPL s may have is the expectation that, because they do all the usual PIC stuff, they think that they really are the PIC, rather than under supervision. Perhaps, particularly for those fortunate to own the aircraft, it’s an ego thing?