I did this. Ouch. I had thousands of songs loaded and wanted to select them all. Pressed CTRL+A and suddenly a dialog showing progres sin tag updating was on my screen. What was it doing? Sheesh, it got through 60 tracks before I could reach Cancel with a clear frame of mind.
A minute of research later and I discover what must have happened (a 99.9999% certain guess). I slipped and touched CTRL+S hot on the tail of CTRL+A.
Now I generally have the tag panel hidden and have never used CTRL+S, opting instead to use actions and the Extended tags button.
Irrespective though having two shortcut keys so close together and the latter so dangerous is to my mind a strong candidate for description as a UI bug.
I recommend that CTRL+S be followed by a confirmation request if more than one file is selected and/or that such a one key nuke tags command be shifted to the less accident prone CTRL+SHIFT+S shortcut for example.