alt Hacker NewsReplace the word "study" with the word "cheat" and it makes more sense. You aren't SUPPOSED to study for an IQ test.
What you are seeing is that if you cheat it helps a little bit. That's not an argument for OR against them in general, except maybe to say that they should be more resistant to this type of cheating.
Even if you're not explicitly "cheating", if your job is more primed around pattern recognition and the like, you might still perform better on an IQ test than someone who works driving trucks. This doesn't imply that the truck driver is inherently more stupid than the person who reads patterns all day.