I just started using this plugin and noticed the same thing. Before using the plugin, if I invoke mover, when it's finished there are 0 files or folders left over on cache. After using the plugin I've noticed empty folders still exist on cache drive after a move. It's not really a major thing I suppose. It just means your shares will always show as unprotected if you're running a single cache drive, even if there's effectively nothing left on the cache drive.