OK, but if you do some work, and make a backup with `tar -cf ../.tars/backup-001.tar .`, then do some more work, and make another backup with `tar -cf ../.tars/

OK, but if you do some work, and make a backup with `tar -cf ../.tars/backup-001.tar .`, then do some more work, and make another backup with `tar -cf ../.tars/backup-002.tar .`, then you also didn't create a new empty directory and retype everything, but you'd still be storing snapshots, not changes. (Which is also one way to think about how git conceptually handles it.)