It’s still an open question as to why trans people are trans, but it definitely looks like something is already different as early as the womb.
But that isn’t important, because even if it were false: Purely for the question of athletics, athletic performance trumps all else.
Medical doctors will still need to know about chromosomes for dealing with chromosomal disorders, and if you’ve had your gonads out you’re not going to get gonad cancer, but purely for gender-related athletics issues, the 80-20 principle applies: most of the “million” things your chromosomes do are the same for basically everyone (and thus the reason nobody is born a literal banana), then there’s the subset of chromosomal stuff which affects athletic performance, then the subset of that subset where the gender interacts with the athletic genes such that men and women with those genes perform differently, and in that subset of a subset the difference can be overwhelmed by externally supplied steroids.
Which is why steroids are banned.
Now, in the specific case in this article, transition happened well into adulthood, and the athlete says:
> Vanbellinghen, 27, whose qualifying efforts were disrupted by injury, pointed out that the retained benefit of taking steroids, even years earlier, is widely known.
> "So why is it still a question whether two decades, from puberty to the age of 35, with the hormonal system of a man also would give an advantage [in competing against women]?
Obviously this isn’t the same as the case of someone transitioning pre-puberty. But, as I say, it’s why some trans people want to transition pre-puberty.