Thanks for the additions. It is interesting to learn that Little Dixie is a post ACW term. It is indeed clear as mud, but to look on the bright side: at least one can't be accused of being completely wrong stating a county was part (or wasn't part) of Little Dixie as long as one provides a criteria and follows it.
The Upper South distinction is one that I had also picked up on. There are/were some very substantial cultural differences in the Upper and Lower South. Much of this appears to be linked to geography and climate. As a generalization, individual families tended to migrate roughly due West over generations. By staying in the same latitude bands the familiarity of the climate probably eased concerns about starting over. Of course the climate became substantially different once the Plains were reached, but that is primarily a post ACW migration.
It is interesting that Cooper is omitted in those references, but included in Hurt's 1994 article. I can see why the case could be made to drop it even from Hurt's data: tobacco and hemp production were negligible in Cooper compared to the other counties. This indicates different prevailing agricultural traditions.