It's in Nature, and it's entitled "Genetic patterns offer clues to evolution of homosexuality", by Sara Reardon. As far as the topic is concerned, basically the article says the evidence is weak to nonexistent, but in talking about the individuals studied in one project, she says, "The study looked only at biological sex, not gender, and excluded participants whose gender and sex did not match."
So it seems that they're allowing individuals to define their own gender, but making a clear division between that and "biological sex". Maybe that's their way of staying away from any controversy about how people are treated in society!