My understanding is that the SAT went from being a test of aptitude, to a test of (in large part) acquired knowledge. That’s what invalidated the SAT as a surrogate for an IQ test.
Doing poorly on an SAT or IQ test does not necessarily mean a person is not intelligent.
However, doing really well is an extremely good indicator that he is intelligent.
IQ tests have wildly varying formats. Took two in order once to quality for Mensa. Score differed by 36 points.