Due to National Geographic role in the scientific community it may feel it needs to be more careful skeptical than other media publications when reporting on topics like this. Other media outlets may publish it sooner with less background checks because they are more interested in gaining viewers.
This kind of article and research is controversial and viewers may view it with more or less skepticism solely due to their own beliefs and bias.
Opponents of gay rights may view the article with complete skepticism since it contradicts their own views. More extreme opponents might accuse the scientists of following a liberal agenda to try and create support for homosexuality.
Supporters of gay rights may shelve their normal skepticism about new research because this particular article gives weight to the “homosexuality is natural” elements of their beliefs.