That actually seems worse than what I thought it did. So if I decided I needed to downgrade, my app data would unexpectedly revert back in time and I’d lose data and state produced since doing the upgrade?
Anyway, it doesn’t change the fact there was no warning or explanation. “Hiding user data” should not be something an upgrade does unless there’s some large blinking lights highlighting what’s going on.
And I still don’t know how I’m expected to back up app data now.