[dnanian]

The problem is that you're not dealing with backups sets. Your backup has a single copy of the files.

If you delete first, and then find that the files are unreadable on the source (say during a move/rename), then you have lost the only good files on the destination - all of them. A source drive failure basically means everything is lost.

Acting on encounter means you minimize this possibility (and some ideas we have for the future give you the best of both worlds).