I did encounter this during development, and I think it's because sometimes Blender doesn't create an undo step for operators called by the Python API. For me, it seems to only happen under specific circumstances, e.g., Blender not having any undo history.
Feel free to open a new issue on GitHub if you want to give me more feedback. https://github.com/geedoubleuu/Auto-Sync-Object-Data-Names/issues
Very convenient - 5 stars!
One bug, tho: The Data name auto-changes to match the Object name, but when I UNDO, the Object name reverts, but the Data name does not.