Puberty blockers ARE reversible because, if the person stops taking them, then natural puberty continues as normal. Puberty blockers buy time for the young person to consider what course of action they want to take. Do you know what ISN'T reversible? Letting natural puberty progress - particularly things like the voice breaking for those born male.
Sigh. They are technically reversible. If stopped. BUT THEY ARE NEVER STOPPED. The judges heard evidence and confirmed in their ruling that the vast majority do no stop them. They are not a pause. They don’t “buy time”, the commit a child to continuing down the pathway. You cannot keep repeating the “reversible” lie because it just isn’t true.
“The high proportion of kids that progress from puberty blockers to cross sex hormones is a reflection that puberty blockers aren't handed out willy nilly, but only to those who are most likely to go on to transition fully.”
If this is true, why do they need “breathing space” to figure things out? The fact is this isn’t true at all. I know of children as young as 11 who are on puberty blockers and don’t what what they want. They cannot consent to the pathway they’re on.
The proportion of people who detransition is very low - the stats are few and far between, but seem to suggest 1-5%
The 1% lie comes from a often quoted study from the Netherlands that looked at adults who regretted gonadectomy only. You are correct in saying that stats are few and far between. No one has any idea how many of the girls placed on PBs and testosterone will regret it in the future. As the judges said “this is a live experiment”.
Keira Bell's case is based around, in a nutshell, "I'm one of a small minority who regretted my choice and now I want to stop other people making their own choices, even if it would be right for them".
Wrong. Bell’s case was around the ability to consent to such decisions. Children cannot consent to giving up their future fertility and sex life. Three High Court judges agreed.
This is no more logical than a woman advocating for a ban on abortions because she regretted hers, or suffered an exceedingly rare side effect.
I’m always taken by the fact that with the abortion analogy, it’s always the abortion that is the equivalent. Why? Why is it not the pregnancy? Why is it not analogous to say 11 year old girls cannot consent to pregnancy? You could quite easily say that Keira Bell is advocating for a ban on teenage pregnancy because she regretted hers.
And it’s not remotely comparable anyway. 
I’m always staggered to find there are people who exist who are happy with the prospect of children being given drugs by doctors that will render them infertile and sexually dysfunctional and cheer such decisions because those kids claim to be happy for a while, despite plenty of evidence to show it won’t bring them happiness in the long term.
The only thing that brings me relief in the face of such people like yourself is that three High Court judges weighed up all the evidence that exists and found in favour of Keira. Children will now be protected from the incontrovertible harm caused by doctors for the sake of an ideology.