Yes, they're very efficient. It's an excellent use of vertical space, particularly when that space is at such a premium as it is here.

[ Fraser is a fan of bunk beds. Also of bedrolls, which are even more efficient. He's carrying one now, tightly rolled and tucked over the pack on his back. ]

...Mostly.

[ Those luxury cabins are far larger than anything he can imagine a single family needing. Almost an entire village could fit into one. ]

You've never seen them before?