he's not saying - correct me if I'm wrong here, third - that cultural capital doesn't exist, or that it doesn't influence wealth, just that you can't misapply a sociological concept in economic terms. cultural capital has no existence outside its social context.
in a similar sense to how Rothbard and others (nb: see how much neoliberal background reading I've been forced to do to satisfy
@craner) have challenged Mises' concept of "consumer sovereignty" as misapplication of a political concept in economic terms.