Yes but intersex has nothing to do with unambiguously male or female people deciding to adopt an alternative gender that doesn't match their sex. One is a biol

Yes but intersex has nothing to do with unambiguously male or female people deciding to adopt an alternative gender that doesn't match their sex. One is a biological condition of sex development, the other is a social issue, largely caused by the idea that there are certain thoughts and behaviours that are inherently masculine or feminine. So for example, if you're a woman who doesn't "feel like a woman" (actually: at odds with cultural stereotypes of women) you might choose to identify as non-binary. Which is happening a lot more these days, amongst some populations - so I think this could reasonably be called a fad.