Not to throw a wrench in the works, but there were two issues the OP discusses. The other one was the naming convention. In other words, the pupsave-backup user must be informed that the prefix before the dash in the name of the backup connot be altered, and that this will prevent puppy from loading it at boot, or even displaying it as a boot choice.
I think this GUI is going to require a more thorough explanation to cover all these contingencies. For one, only puppy versions that can load timestamped backups with the BKP delimiter can boot it. Others can't unless the BKP delimiter is removed, so the text would have to be tailored for individual pups. Of course Bookworm doesn't have this issue. Perhaps no new pups would have that issue, but I don't know because I don't how all the developers configure their builds.
The GUI might have to say something along the lines of:
You now have a choice whether to the compress the backup. For future bootup purposes, a backup file/folder can be loaded at boot if located in the search path of the bootloader. However, choosing to compress now would first require uncompressing before attempting to load at boot,. NOTE: For some puppy versions, particularly older ones, the BKP delimiter must be removed from the name of the backup save in order to be seen by the boot sequence, and the prefix before the dash of the file/folder name must remain consistent and read [USE APPROPRIATE CODE TO DETERMINE THE SAVE NAME]