Why are my filtered out files and folders not deleted from the destination?
When a file or folder is filtered out, or unselected in the file & folder selection tree, you are explicitly telling SyncBack to ignore those files and folders. Because those files and folders are now being ignored (they are not part of the backup or sync) then SyncBack does not see them and therefore they are not deleted. You must manually delete those files & folders from the destination. Or, delete the backup completely and repeat the process (this time, the files it is now ignoring will not be copied).
In V8, an option to delete an entire unselected folder was introduced. Right-click on the folder (which must be unticked/unselected) and select Delete from destination (or source, depending on the profile configuration). When the profile is next run the folder, and everything in it, will be deleted.