I think people thinking about children transitioning before the age of 12 to be able to compete in elite sports are missing a key point.
Athletes like Lia Thomas decided that they were women after competing at elite levels in men's sport, and decided to "transition" in their 20s or 40s. And people like Lia Thomas have simply reduced their testosterone levels, and seemingly have no interest in taking oestrogen or having any surgery, they never displayed any transgender signs earlier in their lives.
Put it this way, I question whether any of these athletes are actually trans. They've just seen a loophole that they can use to achieve success.