Thanks for this tech preview.
I did three tests up to now:
"regular" dup = zypper dup "super" dup = env ZYPP_SINGLE_RPMTRANS=1 ZYPP_MEDIANETWORK=1 zypper dup
test 1 notebook: lock libreoffice, regular dup to get snapshot 20210830, remove lock, super dup to get libreoffice update.
test 2 desktop: super dup to get multimedia packages update from packman.
test 3 notebook: super dup to get snapshot 20210831. desktop: regular dup to get snapshot 20210831.
All tests were successful. On test 3, the download with super dup was four times slower than regular dup. The snapshot was fresh so the "additional mirror rating" must have made a poor choice due to the ongoing mirror syncing.