Why would anyone really benefit from just a few hours off their phones?
That's like saying not eating for a few hours makes up for eating 4000 calories at dinner.
maybe it's more like banning smoking - stopping a smoker for 8 hours a day would definitely positively impact their health, even if they find it incredibly annoying.
It could encourage face to face socialization during those hours, which could improve mental health.
Maybe there is a difference in phone addiction management if they are allowed to use it every 45 minutes and if they are forced to be abstinent for 7 hours straight.
I personally would've guessed many immediate positive effects just from a phone ban in school, TFA claims they have a measurement against that.