When I open the same project on my Mac Scrivener 3.1.5, make a change, then close the project, my backup settings produce this filename:
Godsfall-bak-2019-12-14T01-56.zip
Doing the same in Windows Scrivener beta 31 with the same backup settings produces this filename instead:
Godsfall.bak2019-12-142T01-56.zip
Note the dots used by the Windows beta instead of the dashes used by the Mac version.
These need to be consistent – many of us store our backups in a common synced folder, and these naming differences disrupt sorting by name to easily determine the latest version.