See, this is actually one of those racist dog whistles that is meant to stir up a certain target demo (white nationalists), and is meant to get people talking about it (so as to ignore other more important shit).
This "discussion" actually popped back up in 2016-2018 when Douglas Murray wrote a book about it. It's all fucking pseudoscience of course, just as IQ itself is pseudoscience as an actual definition and measure of inteligence.
But because rich whites do a lot better at it than poor brown people, it's very popular in white nationalist circles.
But if you just call Don Jr a racist for this obvious dog whistled racism, they flip their uno reverse victim card and cry about censorship or some shit for the next week or two.