"My links show research that specifically says this is not true."
The researches show that there's no evidence of the importance of genders on parenting, and I agree.
That is quite different than saying exposure to people of both genders is not important. It is important just as it is important for children to be exposed to people of different age, ethnicity, culture, opinion, and such. This exposure helps them build complete mental models of how other people behave, which is important for the development of empathy and self-image.