You are aware that an autism (or ADHD, or any other similar neurotype) diagnosis would have generally excluded you from treatment as a member of this cohort, right?
I assume "excluded from treatment" in this context means someone not receiving puberty blockers and/or cross sex hormones.
I should imagine/hope that anyone with autism who was struggling with sensory issues and/or their body changing during puberty would have been given treatment appropriate to their autism (e.g. Occupational Therapy to help with any body disassociation that may have resulted from this), following a differential diagnosis. Hopefully that's how things will progress now too, rather than social transition happening as a first step i.e. a differential diagnosis to work out what may be the root cause of the distress without making any changes to pronouns etc.
As in, it is literally impossible for the older stats to reflect the neurodiversity of trans people because almost no neurodiverse trans people were allowed to get a diagnosis.
A diagnosis of what? Autism-related puberty distress, linked to cognitive processing of how males and females are "supposed" to be and/or distress about their changing bodies?
You'd just get blocked from even starting the discussion from the outset. I know several people who that happened to.
If "blocked" means not socially transitioning as a first step, but instead neutrally exploring someone's distress without any presupposition that they "are trans", this is a good thing. It doesn't have to be confrontational or dismissive. For example, a counsellor could use no pronouns at all for the child, meaning that there is no affirmation of preferred pronouns but equally no use of sex-based pronouns. Instead, open questions could be asked to unpick more about how the child feels about themselves and what they are struggling with.
Ableism and transphobia go hand in hand, always.
It's not clear what either of these is in this context. It's not ableist or transphobic to understand and meet an autistic child's Speech and Language Therapy (SALT) needs. It's to be expected that autistic children may need support in this area, making sense of all the information about the difference between the sexes and how this is connected to sex-based cultural expectations and limitations. And how it feels if you don't meet those supposed "standards" (and perhaps learning that most people don't), especially if you're already feeling angry/confused/sensory issues about your body changing during puberty.