@Corjan-Meijerink "Autosave plus ask-on-exit" is potentially confusing (as I found!).
I see now why it did what it did. But if it only "sometimes" asks on exit, that's confusing - and people might come to rely on it to deliberately undo their changes. Especially confusing if the discard only discards since the last autosave, which is I how understood your explanation.
Would it be a huge architectural change to have it ALWAYS ask for save on exit, and if the user says no, undo the autosaves? That would be consistent with how, say, Microsoft Word/Excel/Powerpoint works. And it's great for those of us who go into a route, fiddle with it, then change our mind and want it put back the way it was (without messing around recovering from separately saved backups).
You could have a switch sometimes to always ask (like Microsloth Office), or to always silently save both in-flight and at exit (like IOS). I can see uses, and users, for each of those options.
A third variant is to autosave, and always save on exit; but have a Revert button which takes your route back to its state when opened (if pressed before closing).