Quote:
I am not sure if this is due to the RDC Guidelines for FTP, [...]
Actually, it is due to the lack of guidelines. A part of the FTP servers allows non-empty directories to be deleted, the others do not.FileZilla Server will throw an error if you try to delete a non-empty directory directly. Thus FileZilla has to play it safe and delete contents one by one.
I have proposed a change to the developer before: First try to delete the directory directly, and only if you get an error do the walk.