I don't see it as a strawman. The comparison here is a program breaking compatibility with a file _used by another program_. If vim and neovim undo files are incompatible, why does neovim delete vim's file instead of using its own file name/extension and not caring about vim's undo? And why do they use the same subdirectory even? To me it is a case of a program deleting cached files of another program, which, as a user, I see as deleting user data that said program should have touched.