Hmm, these 'similarities' sound basic and predictable imo, rather than striking.
It's not unusual that children - or even adults - would blame the other person after denying it all. And in X's case we know that it's possible that Y in fact did the actual killing and she had no part in the practical action of stabbing. (Obviously she was involved in the planning and intent.)
It's also not unusual that children would act oddly in police interviews. And do we know for a fact that X was 'void of emotion' and confident in her police interviews? We know from Y's barrister that X laughed a lot; that's not void of emotion.
Btw something you said on the last thread I meant to respond to but it was finished:
In addition to this I respect the reasonable adjustments for Y, he has a diagnosis, whether people agree with it or not he has it and legally it made sense to support him through the trial. However girl X does not have a diagnosis, she has traits which many people have and will never even be assessed because they simply muddle through life. Girl X, undiagnosed should not have had any adjustments based on ND, just my opinion
I know they have said that Girl X "has traits of autism and ADHD" but I have wondered for a while now if that means she has traits of autism and she also has ADHD (diagnosed). It's ambiguously worded but that interpretation makes the most sense to me, because it's odd to say someone has traits of both with no diagnosis. Diagnosing someone as having ADHD with traits of autism IS something that is frequently done however; it what was said about my daughter until she was eventually properly diagnosed as having autism as well as ADHD from a specialist team after a thorough investigation.
Even if X only has traits of both, I think it's not just acceptable that she had 'reasonable adjustments' during the trial, but imperative. Because she's a child, and because schools for one are supposed to work on the basis that you accommodate the needs regardless of if there is a diagnosis.
ETA: And on the subject of autism and ADHD, we now know that Brianna had both.