The issue hasn't been switched, but Razib didn't (and usually doesn't) optimize for resistance to misinterpretation in snarky pseudo-correction comments.

Razib and Eliezer were talking about the ability to score embryos based on genomes to select for IQ. To do that, one would need to know alleles responsible for a a substantial fraction of the population variation. Genome-wide-association studies haven't found those for IQ, where they have for, e.g. skin and eye color. Rare retardation-causing alleles that collectively explain less than 1% of that variation are a sideshow for prediction of population variation, the causes of normal variation differ. So meaningful embryo selection is feasible for skin color, but not for IQ. That's not esoteric, that was the concrete point in discussion that inspired Razib to mention the state of the search for IQ alleles.