I think you could argue that within the intersex category, there is most likely a bimodal distribution. There will be a mixture of male and female characteristics, but the majority of individuals in the intersex category will still fall more towards the 'female' or 'male' ends of the spectrums, resulting in 2 peaks. However, outside of this sex is functionally binary because there are two options; male or female. Intersex is not a third sex.