I notice I see this kind of thing for girl groups a lot more than I see it for boy groups. I think it's partially unconscious bias against women by assuming they can't get along or something.
I don't follow Red Velvet closely, but didn't they choose to live in the dorms together for a long time instead of choosing to move out?
I don't know RV that well, but from what I've seen, people tend to treat bgs like people more than ggs, talking about their personalities more and stuff