It is not possible to do this "accurately". At such a young age it can only be done in a very small percentage of cases. Many will not receive the treatment they might have benefitted from.
I don't know where to start on that one. First, you continually side-step the huge questions on whether there can be
any "benefit" from pre-puberty castration, never mind benefit that could possibly outweigh the huge harms which you repeatedly ignore.
Second, as you now acknowledge that it's not possible to predict which children will still be wanting to pretend they are the opposite sex when they are adult, what is the point of any of it?
Third, we are now in a climate of "affirmation" where no attempt is made to explore the child's mental state - that would be transphobic - and
all the children who are brought by their parents to these clinics are "believed". Rather than this elusive child who might have "benifited" from pre-puberty castration, loss of sexual capasity, fertility, IQ points, yadda yadda, but was denied, we have children who in all probability would have given up the whole idea if left to go through puberty being subjected to these harms.
In many cases it is not the best treatment, but sometimes it is.
While disputing that this could ever be the best treatment, given the enormous harms and the intangible, over-hyped "benefits", surely you understand that when it's not possible to accurately stream these children into the ones you believe would benefit and the majority who won't, how can it be ethical to go ahead? Even with some gatekeeping you're going to be damaging a lot of children unnecessarily. With the current affirmation model, you're going to damage them all, the many whom even you acknowledge won't benefit, as well as the few you persist in believing are better off castrated and sexless and sterile with fragile bones and a lowered IQ.
We shouldn't expect that; but some kids do.
As opposed to playing up to the therapist, doing what they think mother wants, doing what they think will get them attention, get them lionised in the stunning and brave category, or get them out of this scary puberty thing they don't really fancy? How do you tell?
It would be interesting to see whether in a less gendered society, it will become harder to identify transkids early. I guess that is certainly possible. Such a society would however be easier for them (and everyone else) to live in, so overall a good thing. Unfortunatly, most of the opposition to transgender issues comes from more rigidly gendered places, and from people who insist on more rigid gender norms.
Transkids. There should be no such thing. It's like a vegan cat. We all know who is making the decisions.
Children should be free to play, dress and express themselves however they want without amyone ever suggesting to them that their preferences might mean they need to be castrated and become medical patients for life. If they choose that for themselves when their brains are mature post-puberty, then that is their choice.