Unlikely or not, sod's law dictates that the worst possible version of the scenario outlined in that Twitter example will crop up. And more than once.
There don't have to be many young men like this to make a big detrimental difference to women's sport. This is because if the men have any talent, they will be at or near the top of the rankings in women's sports.
Pubertal testosterone is the superserum, but two previous little bursts bake in the male performance advantage. The infrastructure of superior strength etc is always there. This study shows the performance difference between prepubertal boys and girls. Boys outperform girls on every measure except balance and flexibility.
https://www.researchgate.net/publication/224914505_Physical_Fitness_Differences_Between_Prepubescent_Boys_and_Girls
The kids on the study were 10 or 11 years old - so the boys would have been before Tanner stage 2 which is the cutoff point in the policies of some sports bodies.
The muscle cells, the heart and lungs, the oxygen delivery system, the ligaments of a boy are different to those of a girl.
CAIS males, who don't even get the benefit of the two mini-puberties because they are completely insensitive to the androgens their bodies produce, are nonetheless overrepresented on podiums for women's individual sport, compared to the incidence of this condition in individuals in the general population.
The Castrati lived long lives and, given the state of the science of medicine in the Renaissance era, they must have been pretty healthy. They travelled, they sang for a living. Bel canto singing demands stamina and basic good health. They fought duels, had affairs. They were taller than the average man. They were definitely not invalids.
Duelling ref here.
https://en.wikipedia.org/wiki/Caffarelli_(castrato)
A policy which excludes males from the female category based on male pubertal development still accepts a degree of unfairness to women athletes.
And it doesn't make sense. It's still attempting to establish eligibility for the Women's category by irrelevant factors like appearance, or identity, rather than the factor which is significant, ie sex.