I know that. I'm just saying its redundant, and even confusing, to add a third option. Your comment example, "born as a man, fine w a man", itself only really had two variables in it.
Cis and trans Intersex folk do exist. I assume that's what the option is for. I'm perisex (not intersex), so many other actually intersex folks could explain it better than I can, but basically intersex means your reproductive organs, chromosomes, and/or hormones naturally don't neatly fit within the two boxes of "male" and "female". So, for example, someone may be born with a vagina, but also have testes or a prostate or something like that, and the doctor just kind of guesses and picks "male" to put on the person's certificate. The person grows up, is treated as male, and also separately happens to identify as male. And when puberty hits, his body ends up giving him a testosterone-dominant puberty. Because of this, this intersex person may have been born with a vagina, but grew up treated as a cis perisex boy, and also identifies as a boy, so he may identify as cis but not fit neatly into the perisex category we think of. That's my best explanation of it. Someone with more knowledge please correct me if I have fumbled.