Autism and low intelligence and over diagnosing

I think the ASD and other supposed brain "dysfunction" difference in thinking is what can make our children look at the world differently and help make it a better place.  I can't change how I think.  Temple Grandin (severe side of the asd spectrum), John Nash (nobel prize winner with schizophrenia), Jacob Bennett (ASD regressed from talking to nothing in his 2's), Raun Kaufman (diagnosed with classic autism), Carly Fleischman ( writer of 2 books, presently going to mainstream university and still non verbal, considered retarded, behaviour calmed amazingly as soon as she was able to 'voice' her feelings etc), Dr John Hall (diagnosed severely autistic and retarded), parents now are trying harder with their ASD kids instead of giving up on them and many are starting to see that experts were wrong when they said that their child would never be able to do this or that.  Many experts have been extremely incorrect about the ASD child's intellect.  Children originally diagnosed severe and retarded have made massive strides into the mild side of the spectrum with people constantly saying "well maybe they weren't in the first place".  This is my experience over the 1.3 years.  So if kids are going from severe to mild or even staying severe and writing books with the help of technology where is this so called wall of misdiagnosis?