You should really read the whole thread. I posted the relevant passages from the new FINA policy yesterday. Another poster and I both provided links to the FINA policy document.
To repeat, the new FINA policy says:
a.All athletes must certify their chromosomal sex with their Member Federation in order to be eligible for FINA competitions. Failure to do so, or provision of a false certification, will render the athlete ineligible.
b. Member Federations must confirm their athletes’ certifications of chromosomal sex when registering their athletes to compete in FINA competitions.
c. FINA reserves the right to include a chromosomal sex screen in its antidoping protocol to confirm such certification.
I dunno for certain if this means swimming sports federations and FINA are going to be "administering chromosome tests to 12-year-olds," because I am not sure what age brackets the FINA rules apply to. But FINA does holds junior world championships where the competitors are teenagers at least as young as 14. So presumably national swimming federations will be testing the sex chromosomes of kids with elite potential as they come up the ranks.
Why does the prospect of this bother you? Sex chromosome testing and other forms of DNA testing are done all the time both in utero and long after birth for many, many legitimate purposes. Such as forensics, to establish paternity and other familial connections, for medical diagnosis, to counsel and prepare prospective parents, to trace ancestry and determine ethnicity. It's not a big deal.
I've personally had testing of my own DNA done several times - lots of people have. Because of my family history and my own genetics, early on in my pregnancies with my own children I had CVS so their fetal DNA could be screened too - and that was decades ago. Nowadays, the widely-available NIPT means sex chromosome and other genetic testing of human fetuses is commonly done from 9 weeks of pregnancy on using blood drawn from pregnant women's arms or fingers in standard ways.
Also, I think if you women generally, and female athletes with a good understanding of why the female category of sport was established in the first place, you'd find that very few are squeamish about the idea of sex chromosome testing - and this holds true for androgynous and butch women as much as for women who are stereotypically feminine in appearance and affect.
If you polled female athletes, I suspect you'd find that many support returning to use of mandatory sex chromosome and SRY gene testing as a way of insuring that athletes with male anatomy and physiology and male physical advantage be kept out of female sports. FINA polled its own athletes before deciding on its new policy, and other sports orgs are doing the same.
Earlier this year, the Cyclistes Professionnels Associés (CPA), which represents athletes in men’s and women’s professional cycling, sought the opinions of its female members before making representations to cycling’s governing body, the UCI, about trans inclusions policies. More than 92 percent of female cyclists in the CPA said they are against allowing trans athletes who are male to compete in women’s events.
Significantly, the last time the IOC required mandatory sex testing for all athletes seeking eligibility in female competition - at the 1996 Olympic Games in Atlanta - the overwhelming majority (88%) of athletes tested said they had no problem with the testing, and 82% said they thought such testing should continue.
As to your contention that "There will be fall out from this if the rules are applied consistently" - what's wrong with the rules governing eligibility for female sports being applied consistently?
The whole reason women's and girls' sports have ended up with so many athletes with male sports advantage like Caster Semenya and Lia Thomas making a mockery of fair competition is because sports policy makers decided to stop applying rules consistently. It's because sports policy makers - almost all of whom were men - held backroom meetings under the radar in which they decided to open up female sports competition to two groups of males who in the past few decades began to demand very loudly and insistently that they be granted special privileges that no other males get - namely male athletes born with a wide variety of disorders of male sex development, and normally-developed male athletes who claim to have an opposite-sex gender identity.