So what you’re saying is that if you use eg smart backup and delete a file locally that it then gets fully deleted from Duplicati backups within some days?
That definitely doesn’t protect from accidental deletions that show up months later. That should not be an advanced user thing for sure. I would think its just an oversight.
According to the following then this would indeed be an incorrect situation or bug as smart backup says it will have a limit for 12 months (There will remain one backup for… each of the last 12 months:)
“any file deleted from the source will subsequently be deleted from the backup when it reaches the retention policy limit.”