> The vim comment seems to suggest that if you don't to the copy, you can't clean up the items

I don't see that extra implication you point. I think you're taking it too literally (perhaps not the ideal wording, yes), but the comment just means what we are talking about. This is, if you don't do the copy, then src and dest are the same, and you *can't* do the cleanup, because it breaks, src and dest being the same.