That quote is from a good article in Nature on how sex is non-binary — my only quibble would be with that “now”. You’d have to define “now” as a window of time that encompasses the entirety of my training and work in developmental biology, and I’m getting to be kind of an old guy. Differences in sex development (DSDs) are common knowledge, and rather routine — and coincidentally, I’m giving an exam on sex chromosome anomalies today.