I doubt it's his biggest gripe(since one can always find something else to complain about on the internet), but it may be the most prominent gripe, since it is mentioned in the first sentence of the "About Jason" box.

To me, it just seems like a very irrelevant piece of information to provide at that point in the text, unless an equally prominent portion of the book is devoted to discussing why being one of the fittest people in tech(as opposed to the four thousandth fittest person, which is still pretty darn fit compared to average) is important.