That seems like a tenuous argument at best. What I got from the article was that it examined both genders, and that women tended to fall into line with this met

That seems like a tenuous argument at best. What I got from the article was that it examined both genders, and that women tended to fall into line with this method slightly more. It would be a different story if it were developed as a method for gauging women's ages, and extrapolated to men - your reasoning would hold then. Forcing the use of "her" instead of "his" is just as sexist. If we want to improve the mental model of the listener (reader) through the use of language, then we should make a conscious effort to be correct instead of argumentative, and say "his or her" or "their".