Gender divide in sports is there to increase participation by giving a chance to women to win as well. There are smaller classes of people who naturally don't fit in either male or female category (eg someone mentioned chromosomes, so people with XXY are usually almost male but not quite): there is nothing contrived about it.

Similarly, people converting have their own sporting characteristics, and we should work to find ways to include them as well.

As such, we need classes that distinguish between different levels of de facto biological advantage: a completely open category would still be dominated by males.

I don't understand why would people find different martial arts weight classes normal, and not even entertain the thought that this might apply to other sports as it pertains to other genetic and acquired traits.