It is not the job if the FA to make up the rules, just enforce them. They are told by the FAA that is the rule. They have no choice!
He probably mouthed off to the FA.
I saw this on a flight recently. A person OBVIOUSLY had the phone on and in her hand. The FA said 'turn it off'. The passenger reported the switch was broken and couldn't the FA told her to take the battery out. The passenger refused. We took off with it on. They were not friendly to each other all flight.
All cabin crew should enforce it or ignore it! Not make it up as they do along. Again, I am sure he got mouthy and ticked the FA off.