Nope, we're just learning to recognize it better, destigmatizing it so more people seek out a diagnosis in the first place, recognizing it's a spectrum and that

Nope, we're just learning to recognize it better, destigmatizing it so more people seek out a diagnosis in the first place, recognizing it's a spectrum and that people with a more subtle expression of autism can still be diagnosed, etc, etc, etc. I know someone in their 50s who was diagnosed recently. They've been who they are their whole life. I know a lot of adults who have similar personality traits that haven't been diagnosed - I don't know how many would be, if they were to speak to a professional, but it's not 0. (I think there's maybe a 25% chance I could get an autism diagnosis, were I to talk to my doctor about it. People have encouraged me to, but I personally don't see how that information would be useful to me.) These adults are the "missing" children from your statistics.