Using IQ as a concept to enshrine intelligence is a terrible mistake IMHO because it encourages this toxic RPG-enshrined idea that intelligence is a number that goes up. That makes it only slightly better than it being just a bool. We don't even begin to know how to measure intelligence or what is in or out of scope when we use the term "intelligence". So to use such a study as a short hand to suggest a country is getting "stupider" or "smarter" just feels like shamanic rune throwing.

We could suggest that IQ is a measure of intelligence but I would argue that IQ only matters if you're applying to university which also gives it this correlative value of "wealthy" and "parents that care" if you're cherry picking economic outcomes which makes it hard to pick apart as a vacuumed characteristic. It also is a very narrow measure given that the breadth of human endeavour requires a lot more types of intelligence than just shit-hot pattern matching.