I think Nick Matte is oversimplifying, which doesn't help. It can be argued that 'biological sex' is something we identify and classify, and to which we've attributed certain meanings, but that it's possible to reclassify and to atttibute different meanings to the same empirical observations.
And that's all very well but if we wish to do that, we have to start from our current position, which is a history of tens of thousands of years of oppressing half the population on the basis of those observations. I'd like to see liberation from that oppression before I accept wholesale reclassifications. Perhaps Nick thinks reclassifying will lead to liberation. I disagree.
Once upon a time I hoped that the transsexual phenomenon could be part of that liberation by problematising sex classification. However, the current Stonewall agenda suggests a doubling down on a binary I consider oppressive.
As for Riley... I'm happy to agree with this single phrase, but from Riley's other statements I'm not sure Riley understands what 'social construct' means.