Sounds like an FA imaginary rule. I've been told before that I couldn't wear earphones during takeoff and landing. When I asked the FA about it, he said it was an FAA rule. I politely asked if it was a new rule. He said no. Then I asked why no other FAs enforce this. He got very testy and suggested that he might toss me off the flight. I backed down (in fact, I remained polite through the whole thing.)

My point: some FAs make stuff up. Report it, as the upstream commenter said. Not as a complaint, but as a clarification.