i can confirm, that the Pd-0.55-2 images were built on a Mojava VM,
whereas the Pd-0.56-2 were built on a Monterey VM.
both were using the identical hdiutil create
invocation to build the
DMG, but apparently it does something different on newer macOS.
It does seem likely that Apple would have changed the default filesystem for .dmg files created by hdiutil to APFS, but I think it is still possible to specify HFS+ by using the ‘-fs HFS+’ option with ‘hdiutill create’. I have no idea if the latest Mac systems can even mount HFS+ disk images. Removing that capability would be exactly the sort of thing Apple loves to do…