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It is becoming increasingly clear that for many traits, the genetic effect sizes estimated by genetic association studies are substantially inflated for a few reasons. These include confounding due to uncontrolled population stratification, such as dynastic effects, and perhaps also genetic nurture[1]. It is also clear that traits strongly mediated through society and behaviour, such as cognitive ability, are especially strongly affected by these mechanisms.
You can avoid much of this confounding by performing GWAS on only the differences between siblings ("within-sibship GWAS") or between other pairs of family members ("family GWAS"). When you do this for cognitive ability, you find substantial deflation: heritability estimates decrease by around 45%, and the effect sizes estimated in population-level GWAS only correlate with these more direct effect estimates by about 0.55.
Does your analysis take this into account, for instance by using effect sizes estimated by within-sibship/family GWAS? If not, it would follow that genome editing would yield substantially lower increases in IQ than you estimate.
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Genetic nurture is a little complicated. The classic example in the GWAS context is parental genetic nurture. Here, you find an effect of a genetic variant on a trait in people, but the actual "direct" effect manifests only in those people's parents – one of whom must carry the variant, otherwise it would not be observed in the people in your study – and affected how they nurtured their kid, which then affected the trait you were measuring in their offspring. Genetically editing such a variant into an embryo would thus have no effect on that embryo when they are born and develop.
The "Black Death selection" finding you mention was subject to a very strong rebuttal preprinted in March 2023 and published yesterday in Nature. The original paper committed some pretty basic methodological errors[1] and, in my opinion, it's disappointing that Nature did not decide to retract it. None of their claims of selection – neither the headline ERAP2 variant or the "half a dozen others" you refer to – survive the rebuttal's more rigorous reanalysis. I do some work in ancient DNA and am aware of analyses on other datasets (published and unpublished) that fail to replicate the original paper's findings.
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Some of the most glaring (but not necessarily most consequential): a failure to correctly estimate the allele frequencies underlying the selection analysis; use of a genotyping pipeline poorly suited to ancient DNA which meant that 80% of the genetic variants they "analysed" were likely completely artefactual and did not exist.