Maybe I haven't been on the static web in too long, but my memory is of pages refreshing whenever you hit back after some amount of time. Do they have a longer cache option? I don't see anything in their JS that suggests saving state.
It's a modern anomaly with JS frameworks that we've hacked and over-stretched the DOM so far past its original design that basic things like going forward/back need explicit JS handlers that rarely work all that well. You shouldn't need any state in JS to store basic navigation. It didn't used to be that way, and arguably shouldn't be that way for simple text-based sites like this. Maybe it's just becoming a lost art these days =/
Just don't look at the HTML :D