Time Machine backup volumes are now explicitly disallowed as source or destination selections on Big Sur. We're not planning to offer support for cloning to or from volumes that are [s]flagged as used for Time Machine volumes backups.
Does that edit of Mike's statement clarify the meaning of his statement? That is what I heard when I read it. There are sound reasons for that change...
Apple has always recommended that any drive, partition, volume used to store Time Machine backups be dedicated for that sole purpose.
If more than one computer uses the same Time Machine backup drive, each computer's backup data set will be contained in a separate sparse disk image.
with the advent of APFS Time Machine backups have begun storing changes as APFS snapshots which could make cloned Time Machine volumes tricky and perhaps unreliable
add encryption to the data set and the chance for error increases geometrically.
Why should CCC reinvent Time Machine's wheel? If you want a backup Time Machine data set simply specify each of the drives/volumes in TM as Time Machine volumes and TM will alternate backups to each selected drive/volume. You can even include an off-site Time Machine volume that would automatically be updated when it is connected and TM will nag the user if it goes too long without its being connected.
If we knew what it was we were doing, it wouldn't be called research, would it?
