Lots of apps implement this by autosaving to a different location from the manual save. So autosaves overwrite each other, but they don't overwrite the user's explicit choice. On loading a save, if they detect the autosave is more recent than the manual save, they offer the user the choice of which one to use.
Microsoft Word has had this since the 90s (with slightly different presentation from today, and definitely without sophisticated history tracking). Their computers used to fail (blue screen) much more regularly. It's not about web apps vs desktop.
Exactly. The original problem was "people are losing all of their work cause they're not saving." So you autosave every minute or so to a separate "recovery" location, then if the user exits without manually saving, on next startup you give them the option to continue from the last autosave if that autosave is more recent and not identical to the last manual save. Doesn't require full change logging, and only requires one "last autosave" at any given time. IIRC this is how your Word example from the 90s worked.
Microsoft Word has had this since the 90s (with slightly different presentation from today, and definitely without sophisticated history tracking). Their computers used to fail (blue screen) much more regularly. It's not about web apps vs desktop.