That's true if you think there zero circumstances that female sex people should be kept separate from male sex people. If you believe that then what you say is correct. If there are any circumstances where the above is not true then you would need tight definitions. It's certainly a bone of contention right now eg sport, prison, etc.
If you have tight definitions, then wouldn't that mean you have to ban all trans women from every woman's bathroom and changing facility because you don't think Anthony Joshua should be able to change his gender today and go toe-to-toe for the women's heavyweight championship tomorrow.
For niche interests like sport, I would be happy to defer to sports scientists. Who might think that there are some situations when it's appropriate to discriminate and some situations when it isn't. I mean, they probably wouldn't let me go toe-to-toe with Anthony Joshua for 12 rounds either.
Jumblegraws, I ducked out of that Suzanne Moore thread as I felt I was annoying everyone, but I did see your apology and I am grateful. <3 one love, don't worry about it, water under the bridge etc