Classic,
JUUD is just reiterating the training CC receive whether you think it accurate or correct or not. I believe we are ALL employed to follow the rules and to enforce them if necessary.
Whilst I agree I am unlikely to crack out the bondage kit for a passenger not turning off their mobile there are other ways that the crew in the Flight Deck can help to make our colleagues in the back lives more easy - showing a united front on PPRuNe could be one of them.
Everywhere has to draw a line and, I say again, it is not up to Flight/Cabin Crew or the passenger to discern which electrical equipment is okay and which is not and which signs should be obeyed and which not, that is the preserve of the relevant department within the airline - the rest of us just do as we are told.