The first three posts in this blog used the two words 'identification' and 'diagnosis' to describe two different things.
Identification is the process by which someone identifies or is identified as autistic. This should not depend on a formal diagnosis - people can self-identify as autistic. If they do, it is not for me to disagree with that. But identification may also be done by someone else, including a professional person. So, I would say that my daughter-in-law and wife identified me as autistic, then I identified myself as autistic, then psychologists identified me as autistic, and so on.
Diagnosis, on other hand, refers to a distinct moment at which the medical professionals, in the form of psychologists, use a set of fixed criteria to evaluate a person and give them the label of "autism spectrum disorder". Of course, this term is highly loaded. "Disorder" implies a neurotypical idea of what constitutes order. The idea of a "spectrum", while very valuable in some ways, can in the wrong hands be seen as simply a sliding scale between high and low functioning (this is inaccurate). And the word Asperger's, which used to be a standard diagnosis, is now obsolete.
Luke Beardon, writing in "Autism and Asperger Syndrome in Adults", is quite clear that autism is neither a disorder nor a condition. He also substitutes the word "identification" for "diagnosis". This makes sense to me, but I would also observe that a "diagnosis" is a significant waypoint for many autistic people. Having an "official" diagnosis can (as it did for me) unleash a whole revision of oneself that is hugely beneficial, if challenging.
The problem with "diagnosis" is that, for those people who do not have one it may seem as if they have been refused membership of an elite club. Now these people may or may not accurately self-identify as autistic by medical standards. The point is though that they do so identify which, as far as I am concerned, makes them de facto autistic. At least, I have sufficient respect for them not to want to question the fact. I would never comment on a person's diagnosis or lack of it.
Another, more ironic, problem with the word 'diagnosis' is that many medical professionals are, to say the least, sceptical of its use in this context. Some doctors I know have even cast aspersions on the whole discipline of psychology, regarding it as not proper medicine. The irony here is that the medical/social model of disability is often cited in relation to autism, but many on the medical side would actually agree that this is not a medical diagnosis at all!
Words matter, and all the more so in this context, because autism is such an evolving field. I still struggle with what to call myself. If I say "I'm autistic", then people often react by comparing me with autistic people they know (either in real life or through the media) and fail to find sufficient correlation. If I say "I'm Asperger's", most people seem to find that more believable, but the problem is that other autistic people and the DSM-5 do not approve the term. In fact there is quite a backlash against people calling themselves "Aspies", I've noticed. If I say "I'm neurodivergent" then people find that easiest to accept, because it doesn't sound medical at all but rather a kind of attractive eccentricity. But now I have strayed too far from autism and invariably find myself having to qualify the statement.
A note - "neurodivergent" is the state of my brain, while "neurodiversity" is a description of humanity. Any group of people is neurodiverse, because everybody thinks differently to some extent. Neurodivergence, on the other hand, refers to a "hard wiring" which is permanently divergent. You can see how quickly these terminologies become confusing!
So, I will continue to use "diagnosis" to refer to the moment two years ago when I was pronounced autistic by professionals. But this was just a way marker. I am now "identified" as autistic, both personally and professionally. So "identification" is my preferred way to describe this state of affairs.