There are athletic sex differences even amongst prepubescent children, mostly caused by the testosterone surge in utero.

See https://womenssportspolicy.org/pre-puberty-male-female-child....

Quite a biased source, no? This doesn't provide evidence that these differences are biological. Boys are much more likely to exercise than girls due to social norms: https://pmc.ncbi.nlm.nih.gov/articles/PMC10478357/.

The test is used for initial screening only.

Presence of SRY in an athlete registered as female means further tests must be undertaken, with permission of the athlete, to determine eligibility.

Absence of SRY means the screening is passed and the athlete is eligible to compete.

They're not all taking banned substances. Case in point, Hergie Bacyadan and Elis Lundholm competed in the last Summer and Winter Olympics respectively.

Both Hergie Bacyadan and Elis Lundholm has not undergone any hormone replacement therapy or surgery, and competes in the women's divisions. Their status as trans men has nothing to do with their eligibility to participate.

This would be like if two trans women, who has not undergone any hormone replacement therapy or surgery, would compete in men's divisions.

That athlete was excluded from the women's competition on the basis of having male physiological advantage. Exactly what the Olympics are now doing.

Androgen insensitivity syndrome means that her cells do not react to testosterone. What male advantage is there if her cells don't react to testosterone?

Soundarajan's androgen insensitivity was reported as being partial (i.e. PAIS, and not CAIS), which implies some degree of testosterone-driven masculinization.