I just looked for about 10 minutes on every Autism website that was genuine for evidence that self-diagnosis is okay. I've seen a lot of sites that accept self-referrals but the second step was always contacting a medical doctor. I fail to see how anything productive can come from potentially lying to yourself. Yeah, you could be correct. But assuring yourself you have something isn't any healthier than living without a solution to your potential disorder.
Autism website that is genuine? What do you mean by genuine? Is the NHS website not "genuine" enough for you? The national autistic society website not "genuine" enough for you?
Both of those discuss adult autism diagnosis as a "mixed blessing" and only nessecary if you have current difficulties that could be resolved with accomodations/supports or need treatment for other problems to bear in mind that you are autistic, or need to get rid of a previous misdiagnosis.
Being mistaken is not the same as lying to yourself. And if you have something similar like say ADHD and social anxiety, which, symptomatically, can be kind of like autism, then a lot of the advice and support for autistic people will be very helpful to you, even if not all of applies. If you are right, most of it will apply, and it will help you.
Assuring yourself that you have something when you actually have it is very helpful.
You seem to be obsessed with the idea that people who self-dx are wrong? But you know that most adults over 30 won't have been diagnosed as children, and girls and poc are generally underdiagnosed, and don't you think that some of them might have noticed?
There are huge numbers of undiagnosed adults out there, and there are also some self-dxed people. Don't you think that those people will be the same people?