Yes, that’s true, but the same arguments can be made about the other regions too. In the heartland, the Minnesota dialect is worlds apart from the Kansas Dialect. Lutefisk is very different from Kansas City BBQ. Cajun in Louisiana and Cuban in Florida are very different from the rest of the South.
Where does Texas Fit? Southern, Heartland or Southwest? How about Idaho or Nevada?.
I just thought that too many subcategories would be confusing