I think you may be able to hold the accomplishments/time ratio constant while varying the quickness of thought. However, the quickness of thought that I'm talking about may be different than what the article is addressing.

For example, in a math class it may take me a while to comprehend each step that the teacher is taking which makes me lag behind the rest of the class, but given enough time to fully understand everything, I can outperform the average without too much trouble. So it can be in the way that I attack problems. I slowly and methodically learn about all of its parts until I finally comprehend it all and then conquer it relatively quickly, whereas others may quickly learn about something but have to repeat the process a few more times to get it to sink in.

Maybe this kind of slowness has nothing to do with the speed at which nerve impulses travel, but it sure doesn't help with job interviews.