While surely there is some genetic component at play there it appears to be primarily motivated by the primate social adaptation system.

This seems like a strange argument, because "the primate social adaptation system" is also ultimately governed by evolution. Obviously a primate group with a social tendency towards incest would have worse survival rates than a primate group with a social aversion to incest, and that social fabric definitely is tied to evolution (unless you mean to imply that our social fabric did not arise from evolution, but I don't think that's what you're saying).

Also, I don't see how this can have anything in particular to do with primates and their social constructs as incest is avoided by all animals, as far as I am aware. It is not a purely human or primate thing, incest is bad for all animals and so they have all evolved via evolution to avoid it. I'd say the Westermarck effect is just the result of that evolution - obviously humans can't directly read genetic code, so the mind assumes that whoever you grew up with must be your close relatives, and that's good enough of a signal in 99% of cases, so that's what evolution went with.