I think that is a reasonable argument, but so is the opposing argument.
The purpose of female athletics is to allow naturally challenged people a chance to compete on equal terms. In this case, the “challenge” is that the female body has characteristics that make it less athletic than the male body.
It is that characteristic that defines whether you can compete in the “female” category, which in a few cases is not what you grew up as.
I don’t know that this woman isn’t a woman, some reports suggest an intersex component here, and that in some more developed countries she may have been made into a male.
But this is not unlike the special olympics, which has a detailed set of rules for qualification; nobody questions whether a person has a disability, but if your disability does not “disable” you in the right ways, you won’t get to compete. The idea is to define a class of people who, if they all trained equally, might have a somewhat equal chance of victory.
I would note however that nothing about sports is really “fair”. Genetics defines limits; being short cuts you out of most professional sports for example, but we haven’t created an under 5’ 6” professional basketball league.
Frankly, I’m not sure why should wouldn’t at least TRY the treatments, and see how much it impacts her. Cutting her testosterone levels now back to the limit for the competition certainly should not put her at a DISADVANTAGE, she’d still has as much as any of her competitors, plus she has years of better muscle and bone development because of it. If she really is “the best”, she will be the best with the treatment — and if she didn’t really have the skills to be the best, then we’ll know that.
Non-female Semenya has previously been forced to compete more fairly, by taking drugs to suppress the output/effect of “her” testes. During those times, Semenya was a non-factor in competitions.
Semenya is basically a no-talent hack, would barely make varsity on a boys HS team. “Her” only claim to fame is beating females as a non-female.
You do present an interesting opposing argument. It illustrates well the difficulty of sorting out this circumstance in a way that’s fair for everybody.