I assume the examples motivate the insight here. I'd draw a slightly different insight from those examples.

The thing is, all the examples are applications of the area of expertise. To be a better athlete, you don't become a physicist, you use physics. The difference between a physics-savvy athlete and an unathletic physicist isn't just physical activity. The athlete is a consumer, not a producer. Going back to school to get a degree in physics might indeed make him worse at sports -- but reading about biomechanics won't. The lesson isn't that adults should learn everything, but that a targeted application of an art/science/skill can be useful even when learning the whole art/science/skill is impractical.