I think most of the album was already mixed in 2006, I don't think "minor additions" means mixing a complete album starting from the beginning.
i dont think it did either, but i think "additions" meant just that. actual musical additions. i.e. frank and bbf. i dont think he meant mixing at all. a little or a lot. coz they hadnt got that far in all probability. note that axl didnt actually say recording was finished.