There is no basis for this claim. I haven't put a number on detransitioners precisely because I have no idea how many there are as a percentage. Nor do you. Which, to be fair, is part of the problem. The lack of any follow up as they put young people thought these largely experimental procedures is really irresponsible. But yes, I've read the same study on detransition. It's worth noting that it claims 13.1% of people detranstition. So if you think the findings of that study were reliable (which I don't, there are numerous flaws with the methodology) then you have to contend with this too. I've also done my homework.

I'm not applying one case to all transgender criminals, I have no idea where you're getting that from. I suppose I would point out that transgender women seem at least as likely (https://www.bbc.co.uk/news/uk-42221629.amp) to commit sexual violence (https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0016885) as other males (which is to say not very, but enough that sex-segregation is justified in some instances).

I repeatedly feel the need to point out that I'm a male. I know that males aren't all rapists. But males are uniquely and asymmetrically capable of harming females. Therefore I think there should be some safeguards in place. Allowing any male who says "I'm a woman," to enter female spaces is not an appropriate safeguard in my opinion.