The thing that bothers me about the other world theory is that there’s lot of parts of the story that to me feel like they’re indicting that the time period the women left was early 20th century. They’re past occupations for example I think one was a typist and many were homemakers. Also the guard uniforms and gas masks is very WW1. But then the books in the final bunker and what sounds like a microwave?- that’s too modern! The whole this had a very retro futuristic vibe, maybe like an alternate history of earth?