I'm with Mike on the definitions. That is exactly how I would define the difference between the two forms.

*laughs* I have this wonderful image of immigrants following the latitude lines across the Atlantic, as they journey to their new home. I wonder if it would have to be reversed for immigrants to Australia and New Zealand. (Southerners do talk about the 'Deep North', in Australia, but that is more of a caricaturing reference to cultural attitudes, rather than a recognition of any linguistic divide.)