Just to add - and because SB knows it had created a FULL archive (that's why it's now creating an incremental/diff archive) already, it could optionally check for the existence of the FULL archive. That was my point.
For single zip it could check for its existence, for no compression - it could check if the dest folder for the last FULL archive is empty, etc.
For single zip it could check for its existence, for no compression - it could check if the dest folder for the last FULL archive is empty, etc.