Duplicati goes a step further than most traditional backup programs.
In most traditional backup programs you can choose between making a full, differential or incremental backup. All backup methods have their own pro’s and con’s. Full backups are easy to restore from, but will cost a lot of storage. Incremental backups are relative fast (only new and changed data is written to the backup target), but restoring can be complex, because every incremental has to be played back after restoring from the most recent full backup.
Duplicati combines the advantages of all backup methods. It behaves as incremental when making a backup: only changed data is sent to the backup destination.
When doing a restore, all backups look like full backups have been performed every time: every restore point contains all files and folders of your backup source. When restoring a folder from your most recent backup, only one restore action has to be performed, in contrast to a “real” incremental backup.
In summary: Duplicati indeed won’t do incremental and differentials backups, it does this better and smarter.