That's what I was saying...AZ and CO are not considered contiguous - and neither are NM and UT.
On the other hand, if one just goes by Chambers which defines contiguous as "touching, adjoining,
near, next (to) in space or time" then I suppose touching diagonally would qualify.
In any case, since all but one of the names can be found restricting oneself to adjoining edges using the proscribed number(s) of cells and the other one cannot, I think it's perfectly fair as it is.