This sounds like what a flight attendant would say to avoid responsibility. The ask is not for policing all the passengers acting like children, the ask is about enforcing a policy their employer set, i.e. doing their job.

For a flight attendant in J where there are maybe 8, 16, 20 passengers, it would pretty obvious, if they have ears and are working the cabin, who is watching a movie/playing a game without headphones.
They can even blame it on corporate... "Per AA policy, you need to put on headphones."
And there would be way less chance for escalation than if another passenger asked/demanded.