Regarding differences between diagnosis in girls and boys. (All anecdotal, but very worthy of actual research.)
I was helping a friend who suspects her daughter is autistic but is in another country. I watched the NAS film on diagnosing girls and it really struck me that, once again, there were actually a lot of stereotypes with in it. In two ways.
I could see that the way girls expressed behaviours were heavily influenced by social stereotyped conditioning. I have taught primary aged children with autism in an sen setting for many years now; more socially aware children with autism are more influenced by stereotypical social conditioning. Those who are much less able to communicate and socialise behave in similar ways between the sexes. Always exceptions to the rule, but I've taught many boys who actually are also able to 'mask' their autism.
At the same time, a stereotype was being presented that I found compelled to challenge as an absolute truth, as so many of the girls I know with autism didn't fit that mould. And I could think of many boys who did.
At the same time, it's a stereotype that could aid diagnosis for some girls who are struggling at school.
What struck me most is I could say some of it described me growing up but I know^^ I'm not autistic. Those were the gender stereotyped parts.
We really do need to be very careful not to also stereotype when it comes to girls and autism, as it both does the girls a disservice as well as boys who present in a similar way. (I have seen one boy being referred to psychiatrists to explore gender dysphoria before they got their asd diagnosis.)
I can see how social conditioning would affect boys' behaviour (as it can for all boys) however I also believe more males tend to be diagnosed with other co-morbid conditions (hate that word) such as specific learning difficulties, adhd, motor skill difficulties etc. Talking to occupational therapists and SALTs, it does seem to be that they see more boys in mainstream and at a moderate learning difficulty level. However, whether that's a result of XY or social stereotyping, we of course don't know.
At SLD/PMLD I imagine, simply from my anecdotal experience, the division between the sexes is more balanced.
The big reason why it's extremely important not to stereotype girls and boys in this way rwt autism, is that as soon as they don't fit that mould, to those around them who aren't really experienced in autism, peers, parents, teachers etc, they run the risk of being channelled down the trans route either by trying to find out why they don't fit in and stumbling across things on YouTube or by outside observers.