See Support Thread of same title. Since that one is “closed”, I started this one.
The answer might be “as designed”, but that isn’t a sufficient answer.
I needed to remove all “WM/*” extended tags from among 10636 tracks.
Instead of updating the matching subset, it re-wrote all 10636 files.
I would humble suggest that is a waste of human time, a waste of computer resources, a “risky” approach to the task.