Hi Frank,
The scheduler was added to automatically sync a local copy of a website to a server where the site is hosted. That is not a backup operation, but simply an update process.
A true backup program would record things like Finder meta data, resource forks, owner / group, permissions, ACLs, etc. Yummy FTP does not support any of that because the FTP and SFTP protocols themselves do not (for the most part).
Certainly though, I could add an additional sync mode that would perform a copy to a datestamped folder. If that's all you're after, and are willing to accept that 'backed up' files may not be identical to the originals (due to missing meta data, resource fork data, etc) then it should be doable.