I think what its trying to say is race as a defined biological categorisation doesn't really exist, at least not to the extent its been described in past. The biological variance between humans is more of spectrum than categories.

race as a cultural / social concept does exist though, and that biology certainly correlates to an extent due to geography and how human society has traditionally functioned.

I.e, the cornish are a race, falling under celtic, which originate from Iberia, but is there a modern biological difference to their surrounding English people? Are they more biologically similar to the modern people inhabiting the Iberian peninsula or those in Kent? And even then, are they really all thatthat biologically different from the modern spanish anyways?