It would ask for permission.

Every time you relaunch the app?

It depends on the app whether that would make sense. If it is document centric, then yes. The user should explicitly open every time. If it doesn't make sense for the user to open it every time, it should ask for permanent permission and that should be recorded in system settings where it can be removed.

This seems like it would not work well with state restoration

What would not work? Give a specific example. The app has access to its own state data regardless. If it needs permanent access to one of my folders where I maintain my data, all it has to do is ask once.

Yes, but then you quit the app. How is it going to read that folder again?

It simply reads it. That is the whole point of explicit permission.

Is that not what happened here?

No. Implicit permissions are not requested by the app, and cannot be removed.