I honestly thought IQ tests were abandoned because of their problematic methodology (my kid is 40 so I don't know much about educational processes or schools these days).

I figured, though, that this is like what we call A/B testing in the software biz, where you sample one population group with another using the same testing methodology. So, in this case, the methodology doesn't really matter, even if it is flawed.

Presumably they took samples of people who had access to their IQ scores and retested them. I didn't do a deep dive into their process. There have been a lot of other studies about brain fog. It really does seem like a thing. And the discoveries about Covid's effects on the brain are pretty convincing.

But I agree with both of you about the general efficacy of IQ testing.