As I said, it was my understanding that the correlation between IQ and life outcomes was well-established, and that IQ tests are designed and adjusted to ensure the correlation remains strong. This is a thing, right?

Thus, the hypothesis that the correlation between intelligence and life outcomes breaks down at high intelligence levels suggests that such adjustment would cease to produce IQ-to-life-outcomes correlation.

(Alternately, this whole system may break down somewhat at high levels anyway - I don't know how much difficulty the relative rarity of really high IQ ratings has introduced.)