Again, psychiatry is in its infancy. Many professionals use outdated models or stereotypes in practice. Living as an autistic individual can make it easier to clock other autistic people, because it's rare to meet someone who functions or thinks the same way you do and sticks out like a sore thumb. For example, "thinking in pictures" is not a universal autistic trait, but it's a pretty well known one.

Being easy to clock won't bring the ratio of something up to 1/8 or 1/4 or 1/2.