Here's one for you....The definition of flight time for logbook purposes includes time spent rotors-running on deck whilst pax are getting on and off etc. Co-pilot does not have an ATPL so cannot log P1 on a large twin. Captain gets out for a pee - who logs what?
In practice copilot continues to log P2 or P1/us whilst captain logs P1, even though he is not in the aircraft!