Some companies post fake job openings (that they have no intention of filling) so this doesn't surprise me. They post the fake openings to learn what kinds of people are job hunting, to fluff up their optics ("we're hiring!") and in some rare instances, to get some free labor with mini-projects disguised as interview tests.
I'm glad the article points out the downsides of quiet layoffs. If you make work conditions miserable, your most talented folks will probably cut and run first, as they can find a new job easier than the scrubs.