>it's not really worth fighting, I don't think.

Absolutely.

Yet it's hardly a secret either and something you would expect someone who graduated university writing for a relatively well known newspaper to be able to get right. It's trivial to most readers of English whether they got it right, sure. It's also trivial to get it right and they did not. It looks bad and casts bad light on the newspaper for accuracy and getting details correct. Needless to say there are plenty of details that may not be as trivial to get right but are non-trivial in their effect of your understanding of the story. How does something as batshit simple as this winding up smeared on the WSJ's face in such a nothing story affect the readers' estimate of how often they get important details wrong? That assessment is up to each reader but I'm pretty sure we can all agree it probably doesn't help much.

Very few English speakers (from the U.S. at least) who've graduated college will have been taught this. I worked at newspapers and no one I worked with knew this. It's not a distinction that English speakers are aware of, even at university level, unless they have a reason to know it, like being linguists or knowing people who are Swedish.

If you're a journalist you can't ask a swedish person if you've messed up any details? That's the point. It's so flipping easy to get the detail right.

Have you considered that they knew it wasn’t technically correct and used it anyway because it was the clearest way to get the idea across?