I think it's terrible that they can't sit down inside to eat, tbh.
I went to 2 large secondary schools (7 form entry plus small 6th form at both), and at both of them we could sit down to eat, either in the hall, the canteen, the common room (6th form only) or our classroom (unless it was a science room - but we could go to friend's classrooms if not science). We were never expected to stay outside at either break or lunch; the hall, canteen and library would be open at both bream and lunch, even if the classrooms weren't.
Though, the classrooms usually were.
To be fair, there was never any supervision in the classrooms or the hall at break. Maybe there was one staff member in the hall, but definitely none in the classrooms.
It just worked. Maybe there are less staff overall, so it's not possible? Maybe there are more children with additional needs or allergies these days? I don't know.
It's bizarre though.
If they're all outside, are they properly supervised? I doubt it. But I bet some of the less resilient ones are just cold and miserable.
Sounds pretty shit to me!