An interesting and yet utterly pointless diversion from the original incident. An incident that was totally avoidable regardless of the state of any flashing lights.
A passenger inexperienced in light aircraft operation should not have been allowed to get out of the aircraft with the prop running unless being met and guided by a responsible person outside the aircraft.
Regardless of the pilots claims on briefing the passenger they should have made them sit there until the engine was shut down or as above the passenger was supervised.
The whole incident was avoidable and inexcusible.