I'm a woman who writes mostly men. I do write women periodically, but I just tend to gravitate towards guys. Granted, I do this in real life, too. I'm much more comfortable in a room full of men than I am a room full of women. With women, I never quite know how to relate. I've gotten better at this over the years, but it still holds true.
I mention this because I often worried when I started writing that my male characters wouldn't come across as authentic. I never considered it while writing really. It was more something that other people brought up when they heard. How can you write a guy if you don't know what it's like to be a man? Blah blah blah.
The interesting thing is that when I showed my books to male friends, they never had a problem with it. They got into the characters, really enjoyed them, and no one ever said "this just isn't realistic." However, the girls who read it often would comment on things, saying "this is too girly; you should consider changing it," or that it didn't seem like it would be right for a man to think or say something like that.
When I took it back to my male friends they thought I was nuts for asking.
I guess my point is that I think there is a real concern when crafting a character of another gender about not being authentic, which might lead to one of the reasons why some female characters (or male characters) end up being too stereotypical.
I'm kind of rambling, but I'm just wondering if maybe in author's attempts to be realistic, they might be crafting characters that are the opposite.