It’s such an odd design decision.
I could see ignoring the old undo data or warning before discarding it but just silently wiping it is so user hostile it’s hard to comprehend.
If you ignore it, do you continue allowing edits to the file? Now undo history is corrupt and useless anyway. Or do you disallow editing until the user manually deletes some hidden, implementation-detail file for a feature they probably never use?
If you ignore it, do you continue allowing edits to the file? Now undo history is corrupt and useless anyway. Or do you disallow editing until the user manually deletes some hidden, implementation-detail file for a feature they probably never use?