i'm sure there are many talented .NET programmers who could quickly pick up assembly and become much more productive than you in that language... if they had a good reason to learn it.
you are proving him right by copy and pasting results of a google trawl without any analysis or apparent understanding. "IQ tests are readily accepted now not to be a test for cognitive ability" is a bizarrely strong claim and so is the idea that it is "impossible to separate cultural and environmental influences". I think it's pretty clear that you are just looking for material to support pre-existing assumptions.
his major achievements to date have been in predicting player performance in baseball, an area which he has spent a large part of his life analyzing. Baseball analytics rewards attention to detail and persistence over technical brilliance/advanced statistical techniques. his special ability is really very domain specific, so it's not like we should expect him to be much more effective than other qualified people if he applied himself to different topics...