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).

1. The first time you open an older route that came over from the classic app, the planner works out its real line in the background. Saving that line also set the route's "modified" date to today, even though you changed nothing. That's why it didn't happen again when you retested: the second time, the line was already there. This is fixed in the next update, and opening a route will no longer change its date. Routes that already got today's date this way will keep it, sorry about that.

2. This one is the autosave. A route that is already saved is saved automatically every minute while it has changes. If you leave within that minute, you get the question. If the autosave got there first, the reverse was already saved, so there was nothing left to ask about. That's why it seemed random. If you didn't want the reverse, pressing Reverse again puts the route back the way it was.