The vast majority of people are biologically not fit to work at Google. All he said is because of slight differences in average ability and preferences we should expect the proportion of women in that incredibly small pool of people who are capable of working at Google to be lower than you would assume if you thought there was no sexual dimorphism in traits needed for engineering.

Another example, East Asian people and Ashkenazi Jewish people are much smarter than gentile whites, half a standard deviation to a full standard deviation on average: http://www.sciencedirect.com/science/article/pii/S0160289606...

Because of this we should expect them to be over represented in cognitively demanding jobs such as engineering at Google. And this is indeed exactly what we see. Should we positively discriminate for white people? This does not mean all white people are unfit to work at Google, it just means that on average white people are less likely to have the requisite ability, though many individuals will.