It’s lazy on the schools part.
Rather than work on appropriate boundaries and put effort into shaping rounded dc during difficult formative years they’ve chosen a blanket rule as a cop out.
Is stroking arms and legs ok?
I remember doing this regularly as a child with my friends but some may feel it’s inappropriate now.
As a parent I would not be happy with some random 16/17 year old boys regularly hugging or touching my 11 year old DD.
Just because the actual act isn’t inappropriate, doesn’t mean it doesn’t always have inappropriate meaning behind it.
If you’re on duty with 100 students and you see a couple of groups of students hugging and touching and then one claims to be touched inappropriately, you cannot guarantee that they weren’t.
There has obviously been an accusation which is why there has been a blanket ban.
If you see a student looking uncomfortable because their friend keeps touching them you just remind them that there is no touching.
If it’s harmless touching or hugging then you wouldn’t say anything.
It’s not lazy, it’s about safeguarding children which is way more important.