I mean, come on, think about it. We're talking about sport. We value strength and speed and power in sport because that is what makes almost all sports interesting. Running, jumping, lifting, throwing, it's very difficult to name an interesting sport that doesn't include at least one of these.

If contortion became an olympic sport, sure, women would undoubtedly be better than men. But it would also be slower (mainly for the sake of decreasing injury risk), less varied and less popular amongst males and females. There are far fewer sports, especially visually entertaining sports, that you can build around flexibility. It's simply about the realities of human bodies. All human bodies. The notion that this is somehow sexist is ridiculous.

And besides, this doesn't actually refute the point, which is that male and female bodies are different and they each have their own advantages and that's why we separate males and females in sport. If you want to frame it as, "males can't compete fairly against females because of their flexibility advantages", fair enough. It's the same argument.