The article does allege that a substantial study found a "modest but significant" correlation between first trimester stress and orientation. Saying for consideration that it is a valid finding:

That finding would not even begin to support gfs. He discounts findings of a much higher correlation with identified genetic markers.
To take a theoretical stab in the dark, there could be those who would be at a balancing point because of genetic factors (or other biological factors not yet understood) who are tipped on over to homosexual orientation by the stress factor.

But gfs never backs away from "choice, choice, choice"; so all the stress factor, or any other biological factor, could do, would be to produce an individual who is prone to make the bad choice of a homosexual lifestyle . I won't hold my breath waiting for evidence for that to come together.