Also, “they didn’t disentangle genetics from social issues” is a bit aside from the point: someone born into a lower SES family faces an additional challenge to achieving and maintaining success, be that learned or born. Childhood circumstances can have lifelong effects in the same way that genetics can.

Now, combine that with all of the other things we do know are SES (nutrition, access to resources like tutors, lifestyle & residential stability, etc, which seem quite difficult to ascribe to genetics)…