“Modern geneticists realize, for example, that genes aren’t destiny…”
Exactly. And this realization has resulted in the takeoff in the study of epigenetics. During fetal development, about half of the deterministic choices moderated by epigenetic modification are random. Identical twins are genetically identical only at that moment when the zygote splits in two. Subsequently, they proceed down different developmental pathways. Some of the most striking examples are studies of discordant disease susceptibilities in “identical” twins in cancers, schizophrenia, autoimmune diseases…
So it’s likely that attempts to “encourage” certain genes are going to result in variety of resulting IQs because, by definition, you can’t control random processes.