Well, that's the minimum boundary recommended, and they cite what the Swiss Government guarantees in the shelters. I would assume you'd try to get more, but then your size requirements for such a shelter rapidly grow.

I think it would go without saying that people would have to get used to vasty different living arrangements should the need to relocate to a bomb-shelter arise. Creating a shelter that is fit for purpose in protecting people from the bomb blast and fallout and also providing a suitable living space is an expensive and resource consuming endeavor, the least of which is just getting enough space somewhere.

Seems like plenty, use bunk beds, 50% of floor area is free. It's not a luxury hotel, it's just to keep you from dying.

It sounds like one of those things that could quickly be accommodated by economy of scale, depending on just what's supposed to be done with the roughly cubic meter of space.

They state you only have to be there for 2 days. That sounds pretty inaccurate to me.