It seems odd that you left out the start of that sentence: "All four of these studies, which used diverse, independent populations and tests (or correlates) of

It seems odd that you left out the start of that sentence: "All four of these studies, which used diverse, independent populations and tests (or correlates) of cognitive abilities, have reported significant, substantial genetically-based positive associations of autism risk with intelligence, notably including full-scale IQ..." I think the part of the sentence where they used "diverse, independent populations" and obviously tried to control for effects like income levels in childhood undermines your criticism. More to the point, the studies mentioned were about measuring the IQ of individuals with known alleles for autism. You can attempt to argue that childhood income may have a stronger affect on IQ than autism does, but the studies themselves showed there was some positive effect of Autism on IQ.