This reply fits in with the thread title of "False positives in giftedness identification" but does *not* address the specific question, "how reliable are these WISC type tests in isolating aptitude vs achievement."

Future readers who may select this thread based on the thread's title, may find the following information to be of interest:
1) Comparison of Giftedness and being on the Autism Spectrum (formerly termed Asperger's Syndrome).
2) GRCNE - Differences Between Gifted Children with AS and Gifted Children without AS
3) Davidson Database, Maureen Niehart Gifted children with Asperger’s Syndrome