This seems like the most reasonable answer. It otherwise doesn't make sense that AirBnB would want to lump these listings into a city nearby for searches specifically asking about a particular location.
I'm not saying that's not the root cause, just that it seems like a backwards implementation if so.
I think it can make sense from a business standpoint. It is unfortunate it hurts other hosts who have nothing to do with it. But I would guess this is just temporary.