Same thing happens in some well-known yeshivos every Simchas Torah (minus the kallah). The RY doesn’t seem to mind, or he’d put an end to it.
But the boys don’t see the girls (I don’t think).
What a novel way to cut down on the cost of weddings!
Doesn’t save anything. They show up for the second dance and eat from everyone who has already left 🙁 I really DON’T understand why they show up, if not to let out steam (which has nothing to do with the wedding).