The book's premise was exactly correct, the Dems won Virginia because of DC, Richmond and not the rural southerners. Same goes with Georgia and Atlanta while NC is only competitive because of Charlotte and Raleigh.
That's a very revisionist take on North Carolina. Obama's victory there was as much built on rural areas remaining much less polarized than in states such as Georgia as his massive gains in the state's metropolitan areas. Clinton and Biden both overperformed Obama '08 massively in the metros, but the late-breaking rural slide in the state that was spurred on by the many nationalized tensions of the Obama years, along with exurban stagnation, prevented them from turning the state blue again.
While the rural South is still strongly Republican as a whole, turning out rural Black voters has always been key to Democratic victories there, as Biden and especially Ossoff and Warnock have demonstrated.