I really don't know how you got here. BMI has been raked over the coals (new and old methods) for being wildly inaccurate for anyone outside of a conditional range. IQ does not predict what to expect from a human being.
Those who double down on IQ as being infallible have something to lose if it's proven to be hack. And history is not on your side here.
> BMI has been raked over the coals (new and old methods) for being wildly inaccurate for anyone outside of a conditional range.
No it hasn't.
BMI doesn't work for three groups of people: it makes very tall or very athletic people think they're fatter than they are, and it makes very short people think they're thinner than they are. But, as GP says, that's less than 5% of the population.
Look at all the effort that's gone into improving hiring. And what're the only factors that people have ever found that actually correlate with job performance? Work sample and IQ.
History is very much on the side of IQ realism. Ten years ago people were denying that a general factor of intelligence existed at all, now it's down to nitpicking or argument from ignorance.
Maybe they are crude. Maybe there are better alternatives. That doesn't make them unscientific.