To a certain degree
Diamond merely described how the conditions which increased mortality in NG (ex murder, chronic tribal warfare, accidents, problems procuring food.) were things for which intelligence could be used to avoid. In contrast, the thing that was causing mortality in Europe (ie disease) is not affected by intelligence.
He said nothing about Europeans or Americans eliminating the effect of intelligence on natural selection. That's nothing more than an old trope Social Darwinists like to trot out from time to time.
Intelligent people are likelier than less intelligent ones to escape those causes of high mortality (murder, chronic tribal warfare, accidents, problems procuring food..) in traditional New Guinean societies. However, the differential mortality from epidemic diseases in traditional European societies had little to do with intelligence,
- how much time in school is spent on critical thought? Maybe a section of one or two classes in high school?
- how much time is spent on direct question and answers? The other 97% of the time?
- how much class time is spent learning the skills to start and run a business? Virtually zero?
Then with standardized testing, it's become worse, now you don't learn the subject beyond studying to pass the test so the school maintains funding levels...
Now with common core, where you don't even have to answer questions correctly so long as you can explain how you came to the wrong answer...
Or like the high school I went to, when I was in class there, it was one class room that was reserved for special ed... Now, it's an entire wing of the school.