I bet that most male F's, esp. NF's, have lots of female friends. It's not as socially acceptable for guys to have close, caring relationships with other guys, platonically, I mean. And I think that NF's crave that kind of closeness with friends as well as romantic partners.
I guess it might get tricky when they get into a romantic relationship though. We all know how close two women can get as friends, and sometimes those relationships have a romantic tinge to them (in fact, often) even though there is no sexual element. In fact there exists a concept called the "romantic friendship"....and I think a lot of ENFJ males do this with females who they are platonic friends with. At least, that's my experience with my ENFJ friend. And while the friendship is very special, it is kind of difficult because it's not something that fits into any of society's categories.