Journalistic quirks and numeric versatility

Reading an Atlantic Magazine article, Always Make Promises: Living up to a social contract is inordinately valuable, and there's no pressure to exceed it by James Hamblin, I was just coming to the conclusion that it was just more of what they do so much of today, insubtantial click-bait. Then I came across this paragraph, which did not change my opinion but arrested my attention.

To make the point, Epley told me to think about an oil spill that kills a certain number of birds. I did, reluctantly. "How much should the oil company be fined?" he asked, rhetorically. "Well, if they killed 20,000 birds, they should obviously be fined more than if they killed only 2,000 birds. That's ten times more bird carnage." It's true; I did the math. But, he explained, if you ask people in experiments how much the oil company should be fined, and the people only see one of those numbers, the estimates are about the same.

What is Hamblin doing here with that sentence: "It's true; I did the math." Is he attempting to be humorous, cutesy, self-deprecating, serious?

I hope it is one of the former rather than the latter. But humor seems a stretch, cutesy unprofessional, and self-deprecating too much of a pose. But it seems almost as equally unlikely that he could be serious.

But it raises an interesting question. For me, and I am certain for anyone in many fields or professions, you simply look at those two numbers, 20,000 and 2,000 and without thinking you know that they are an order of magnitude different, i.e. one is ten times the other.

Are there people that actually do the math in order to recognize that relationship? I am feeling a little like the first time I met a person in a developed country (the UK) who could not count. I really could not comprehend how an employed person of a middle age and in other ways competent could not count. Incomprehensible.

I assume that Hamblin didn't actually do the math, that he just knew as one would expect. But are there educated professionals that are not so numerically versatile that they in fact do have to do the math?