I just noticed that my backup archives are HUGE. Checked the database, nothing there (very tiny).
It seems that with the latest version (2.1.3) they/you changed the backups folder (honestly, I cannot remember, whether I defined the old one myself or whether it was done by the plugin) and the old backups folder was not added to the exclude rules. This happened on Nov 22nd (probably when I last updated the plugin).
So yeah, everything is ok - but I suggest if you (automatically) change the output folder of the backup files, you should either move the existing backups there too (which is better), or add that directory to exclusion rules.