When you get down to it, there's not much difference between what men and women can do. Even if on average one gender or sex is more suited to the role, as long as it doesn't involve reproduction, there will be exceptions to the rule. And sometimes even then. Even with physical appearance, if nudity isn't required, there are some people who can convincingly pass themselves off as the other gender. Not so in fiction where your access to the supernatural powers or ability to use the Applied Phlebotinum may depend on your gender. If so there are rarely any exceptions to this rule.