Man, curiousity killed the cat/cured the laziness didn't it? Tested with TagScanner (
https://www.xdlab.ru/en/) on a batch of files, artwork removed on all, size was reduced on all, incl. the FLAC files if that option was selected. Steps:
1. Hit "Program Options" button in upper right corner, then Tags, "reduce padding inside FLAC files after cover removals.."
2. Hit the "Arrow" button in the upper left corner to leave options screen
3. Put the batch of files into TagScanner
4. Hit the graphic "select all" square button
5. On the right pane under "Embedded Covers", hit the red "Delete" button
6. Hit the big "Save" button in the lower right corner. Let the "progress bar" completely DISAPPEAR--will take a while if there are lots of flac's.
Remember that any tagging work done externally will require that the affected files be re-scanned within MusicBee to reflect the changes.