That opinion is unpopular because it is incomplete. SAT/ACT scores correlate with lots of things, not just IQ and work ethic.
Another huge correlation is with family income:
https://budgetmodel.wharton.upenn.edu/issues/2021/9/28/is-in....
Another huge correlation is with family income:
https://budgetmodel.wharton.upenn.edu/issues/2021/9/28/is-in....
The SAT does indeed correlate slightly more strongly with income than the AFQT does, which could show the "gaming" of the test. Only a ~.03 stronger correlation though. Not particularly dramatic.
As far as I can tell, the thing the SAT really correlates with most is the thing it's actually designed to predict: ability to succeed in college, as measured by college GPA. (In particular, the correlation between college GPA and SAT score is higher than between college GPA and high school GPA.)