But, the hypothesis that that GAD is more accurately diagnosed as intelligence increases doesn't require the expansion that all (or even a single other) mental

But, the hypothesis that that GAD is more accurately diagnosed as intelligence increases doesn't require the expansion that all (or even a single other) mental disorder be more accurately diagnosed. Perhaps it'd be better to say "you'd be opening yourself to the hypothesis", which would be more likely to be true. I still don't think the OP's alternative hypothesis is broad enough to support this claim, but it'd be less false on its face.