As long as he's in bed and resting by the curfew I really don't see the problem I assume the players just sit around watching movies or playing video games before they go to sleep so I don't see why having a guy come and sort your hair out is a problem. Think it's a bit of a generation thing the modern footballer is very image conscious and they go out in front of millions every week so want to look their best as well as play their best.
I think 10 years ago it was quite common for a guy to come to the training ground and tidy up a few of the players hair on a Friday after training it made the players happy so Fergie allowed it.
I haven't read that, but it makes diffeence to me, getting your hair cut so you look good during the game. Nah mate, concentrate on getting your performances up to a level they should be at. Get your hair cut in your own time. Not when you are on duty for the club.
I can only assume it was his own time. If i'm away on a working trip the time I spend at a hotel between meetings is my time. If he wasn't getting his haircut you can only assume he'd just be sitting there on his phone and having a chat with team mates or watching a film. Perhaps Mourinho feels they should be bonding more but Pogba seems like one of the more outgoing and liked members of the dressing room.
It's not my cup of tea but hardly warrants a mention let alone getting dropped over. I would have thought I would mean a bit of decent banter which I think is a good thing.