That particular example, though, is a strong one. McArdle wrote: "Warren and her co-authors defined anyone with $1000 worth of medical bills as having a medical bankruptcy". In fact, the paper used multiple criteria, one of which was $1000 in uncovered medical bills. This is not a pedantic difference, so far as I can see; there's a big difference between having $1000 in bills, some of which is covered, and $1000 in bills, none of which is covered.

McArdle didn't distinguish between covered and uncovered bills in her writing, and given the context (covered bills can't push someone into bankruptcy by definition) it was pretty clear she meant uncovered bills. So yes, the author is being pedantic for insisting that something that was clear from context be spelled out.