SAT isn’t an IQ test, and probably all sorts of people took it before they had cultural awareness or a diagnosis that would have lead to different testing conditions had it been taken after diagnosis, let alone the fact that test scores are not comparable.

GPAs similarly not comparable over large time ranges, schools, or degrees without normalization you can’t get.

SAT isn't a perfect IQ test but it's not bad for a first-pass filter. Nearly all who scored 1600 will be bright and nearly all who score 800 won't be.

It's a bit like BMI. Yes, if you're Peter Dinklage or Arnold Schwarzenegger it will be pretty meaningless. But most people aren't and BMI works pretty well for them.

SAT isn't an IQ test but IQ is very correlated with SAT scores.

While edge cases may exist, for the most part, a test score / GPA / anything where the numerator is almost as big as the denominator is a good signal.