My personal approach to any request for me to fly with someone for the purposes of insurance checks, proficiency flying, skill assessment/improvement or formal instruction towards a rating or license, is the same.
I require that the other person acknowledge before the flight that I be PIC, full stop. We will have a discussion about how to work together as a team in the case of an actual emergency and the other person will agree to immediately relinquish control to me when I say "I have control" without questioning the command.
If they are not happy with the above I will politely suggest that they find somebody else to fly with.