I'm sure many FA's would not make a big deal about it, but 'reporting' someone else with a bag that needs to be put up is a bit like telling someone they didn't do their job (obviously mistakes happen) and not everyone would take as well as you would.

And I hate to say it, if the person in 4B wants to endanger themself that's one thing but there was a military upgrade in 4A who would have been the inocent victum in an emergency.