I'm from the midwest and most people who weren't aiming for Ivy Leagues just took the ACT.
Which is an extreme selection bias. The ACT should have been mentioned to provide more context, but the actual argument works without it.
His point was that if you bias the data source, you get results that you shouldn’t project onto the general population. The specific explanation of the 97% disinterest in the SAT is well and truly irrelevant.
In all seriousness, I had never even heard of the ACT until college. The SAT and AP exams were the only tests ever discussed with us.
I suspect there may be more variation in this than geography.