What constitutes biological sex? Just look at nature for the answer. The universe naturally produces male or female in almost everything in biology and is 100% evident in the mammalian class. That balance seems necessary for procreation in the reality we experience. Anything outside that binary is an outlier, a genetic flaw in the DNA code, like hermaphroditism or DSD. It’s similar to a computer code that isn’t perfect and has a bug. That’s how it has always been, and that’s how it will be in the future—anything outside of that is either genetically manipulated by intelligent life or simply an error in nature. There's no such thing as biological sex being a spectrum; that's complete pseudo-science BS created by a new neo leftist agenda.
When it comes to fairness, I don’t mind so much if pre-puberty girls play with boys and vice versa; it's after puberty when it no longer becomes fair. Women’s sports need a clear and objective definition of what qualifies someone to compete biologically.
From a participation standpoint, consider the new generation where now 1 in 5 identify as non-binary. We’re talking about millions now, so they can definitely have their own league. They are quick to claim there are more genders than male or female, yet want to be included in the binary male or female categories when it’s convenient for their narcissistic cause. It makes no sense at all. They have the numbers today to start their own league, go play coed, go play with men, go play with who you identify with, but please stay away from biological females. If you have a daughter who plays sports, this should be a no-brainer.