But going by the Regulations alone as they’re written doesn’t give a complete and most accurate picture. WA’s current DSD Regulations were drafted more broadly than they're actually being applied in real life.
WA is apparently applying the Regulations as narrowly as possible so as to stay in good stead with CAS, to stave off more lawsuits, and to be as fair as possible to athletes with DSDs.
When the CAS ruled on the Semenya case in 2019, it said in its decision (dated April 30, 2019) that it was approving the new DSD regulations on the condition that they would only be applied to DSD athletes who met very strict criteria, starting with having the standard 46, XY chromosome pattern found in most males.
On May 1 2019, the IAAF published a briefing notes and a set of Q&As explaining how they were applying the regulations IRL:
Which athletes fall under the DSD regulations?
The DSD regulations only apply to individuals who are:
legally female (or intersex) and who have one of a certain number of specified DSDs, which mean that they have [all of the following]:
- male chromosomes (XY) not female chromosomes (XX);
- testes not ovaries;
- circulating testosterone in the male range (7.7 to 29.4 nmol/L) not the (much lower) female range (0.06 to 1.68 nmol/L); and
- the ability to make use of that testosterone circulating within their bodies (i.e., they are ‘androgen-sensitive’).
Relevant excerpts from the Summary of the CAS decision in the Semenya case dated April 30, 2019 and released on May 1 2019:
During the course of the proceedings before the CAS, the IAAF explained that the Regulations are limited to “46 XY DSD” – i.e. conditions where the affected individual has XY chromosomes [and]
testosterone levels well into the male range, the normal adult male range, rather than the normal adult female range
and who experience a “material androgenizing effect” from that enhanced testosterone level.
The only way a person can have natural testosterone levels well into the male range and still be healthy and fit enough to be competing at a high level in sports is to have testes, aka male gonads. And to have testes, a person has to have male genetics.
In the unlikely event that someone with ovaries and female genetics were to have T levels in the male range, she’d be really ill due to a life-threatening cancerous tumor.
You're right that the Regulations as written leave room for an affected athlete to have a karyotype other than 46,XY such as mosaicism. But for an athlete to meet all the criteria, most of the athlete’s cells would have to have the SRY gene. Because that’s the only way that the athlete would have developed male gonads (testes) that produce male levels of testosterone, and also would have enough male androgen receptors in good working order to have the kind of physiological response to testosterone typical of males.
Similarly, the Regulations do leave room for an affected athlete to have ovotesticular DSD and mosacisism. But for the rules to apply, an athlete with OT DSD would have to have enough normally developed and functioning testicular tissue to produce testosterone in the normal male range. To do that, most of the nucleated cells in relevant parts of the athlete's body would have to have the SRY gene.
Whilst athletes with PAIS are included under the Regulations, it's highly doubtful that WA would apply the regulations unless they were dead certain that an athlete with PAIS has enough male androgen receptors in good working order to be able to utilize testosterone as males customarily do. The CAS decision in the Semenya case was very clear that the issue at the heart of the 2019 DSD regualtions was not how athletes with female bodies (genes, anatomy and physiology) respond to male levels of testosterone they might naturally make due to a vanishingly rare and life-threatening disorder like a T-secreting tumor, but how athletes competing in women's events with male bodies respond to the male levels of T they make in the normal, commonplace male way - meaning in their testes.