I think the definitive argument is that all those other studies Dr. Soh mentions support what one can see in everyday life. Despite strenuous efforts at recruiting women into STEM occupations, in encouraging girls to select STEM as their majors when going to university, and despite a total lack of evidence that women are being discriminated against in hiring or acceptance at university (rather the opposite) women continue to be underrepresented in the STEM occupations. That's particularly true of the hard sciences. This under representation is due to self-selection, not discrimination. And it means Google attempting to have a 50/50 gender quota would require they hire basically any woman who applied, regardless of how talented they are in comparison with the horde of male applicants.