The first quote you mention is the summary I wrote of "The Psychological Unity of Humankind". The full post contains this section:

Let's go back to biology for a moment. What if, somehow, you had two different adaptations which both only assembled on the presence, or alternatively the absence, of some particular developmental gene? Then the question becomes: Why would the developmental gene itself persist in a polymorphic state? Why wouldn't the better adaptation win - rather than both adaptations persisting long enough to become complex?

So a species can have different males and females, but that's only because neither the males or the females ever "win" and drive the alternative to extinction.

This creates the single allowed exception to the general rule about the psychological unity of humankind: you can postulate different emotional makeups for men and women in cases where there exist opposed selection pressures for the two sexes. Note, however, that in the absence of actually opposed selection pressures, the species as a whole will get dragged along even by selection pressure on a single sex.