You are correct. In fact, I just drove x-country and Outliers was one of the books I listened to on the way. I haven't had the time to cross-check much of the information, as I just took most of what Gladwell wrote as fact (even if this was just an opinion).
I love Gladwell's writing (he writes some of the most entertaining non-fiction around), but it is wise to take some of his more outlandish claims with a grain or two of salt. He takes anecdotes to be almost evidence, especially in Outliers.
I'm assuming the parent was referring to information presented in the book Outliers, which provides a counter-argument to this