That's too absolute a statement. If you're really good at a subject but terrible at taking tests, you can still do really well in a test by pure brute ability. But one of the money quotes from the blog post is:

> When my friends said I was a “genius,” I would sort-of-joke that I didn’t know anything but could score 75% on any test with a Scantron.

Test-taking is an ability that you can train (and, like any ability, some people enjoy exercising it and some do not), which in a select few situations can substitute for mastery of many other skills. Those select few situations also happen to be pretty common in the Western world.

When I was in school I used to joke that my greatest aptitude was for taking multiple-choice tests. I can do well on almost any multiple choice tests by using elimination and observations about the system of the test writer.