True.

Or someone from Left Hand of Darkness, who only assumes male or female reproductive anatomy for a short time every month, and which set of organs shows up varies from month to month -- the rest of the time, they don't have either. Or a species that has one sex, or reproduces asexually. Or an intersex character.

But I get the feeling that 'pick male or female' would be the mods' responses to anything like this, despite the fact that you tell me 'sex-swap with strict gender roles' and my first thought is 'what happens when I poke it with non-gender-binary characters?'.