The tiny effects claimed per genetic variant also call the scientific validity of the result into question. If you use a large enough sample and a broken enough null model, of course you're going to see "significant" effects.

Genetic variants are correlated. If you have thing 1, then we can somewhat predict thing 2 and thing 3 and so on.

Thus the effects are not really tiny. The direct effect of a genetic variant may be tiny, but it is associated with many genetic variants with similar effects.

This is most obvious in the Ashkenazi population, which has been so strongly selected for intelligence that it now suffers from numerous recessive problems. If you have a trait found in that population, the chances are good that you have other traits found in that population.