Must I purge removed images from score, to reduce file size?

As I develop scores, I save 'safe#' incremental-progress files. I was working on a score named "5_work_in_progress.mscz" and its last incremental save was to "work_in_progress_safe2.mscz" (1) in graphic.

I continued work, and along the way added two images into the score's cover page. At that point, I did another incremental save to "5_work_in_progress_safe3.mscz" (2) & (3) in graphic.

I discovered that by adding the images, the score's size ballooned from 24.9Kb to 691.9Kb - which made sense. I decided to break the composition into a) score & b) documentation, where the documentation would hold the images and no notation, and the score would not have said images, and I hoped the score size would return to a less-inflated size.

After removing the images from the score and saving, the file size is little reduced, to 671.5Kb (4) in graphic.
When I opened the score in my OS's archiving software, I find the images are STILL in the score, even though they don't show up in the score...

Do I have to manually remove & rebuild the .mscz file to get rid of them?