Does the "single save" custom game rule = permadeath?

I'm starting a new playthrough, and what I would like to do is set up the rules such that I can't reload a previous save to undo a mistake or a bad roll, but, in the event of a TPK, I restart from the most recent autosave. Is that what the "single save" option does? Or if not, is there a way to do it? I tried looking it up online but I couldn't find an answer.

(P.S. please don't say "just use self control")