I'm reading a book on the links between Capital and Race right now, and it's very interesting.
It's essentially saying that Marx apparently correctly identified the birth of "America" (and colonial domination) as foundational for capitalism, but didn't explicitly put 1492 as the beginning date, but rather much later with the expropriation of land from British farmers (Enclosures) in the XVIIIth century.
So there seems to be this whole debate spanning the XXth century to this day, between traditional marxists and dissidents, about the beginning of capitalism and how important racism is for its creation and maintenance. The tradition, especially among abolitionist marxists and other marxists of color, insists on just that, and it seems like this perspective is gaining prevalence.
I didn't know the intricacies of the whole class reductionism debate, but it is not recent at all.