I'm genuinely curious if you've actually read the article you linked to, given that the line literally above the numbers you quoted says, in large font and bold caps: "Employees don’t get more time off (and may actually get fewer days away from work)". Did it not make you wonder why?

Now if you look at where those numbers come from, this article quotes another article from WSJ (https://archive.is/MVRur) which is also titled "Why You Should Be Wary of the Unlimited Vacation Perk". Hmm...

And the WSJ article, in turn, takes its number from this report: https://www.empower.com/the-currency/work/pursuit-of-pto-res...

Now when you look at the survey, the problem with comparing those numbers is that they are averages for all workers. That is, 14 days without PTO is the average across all companies, not just those that had adopted UPTO. And the 16 days with UPTO is, of course, only for those companies. So the numbers don't actually tell you anything about the effect of "unlimited" PTO adoption in a given company. Those companies where 14 days is the norm are generally not the ones that decide to switch to UPTO because, well, there's no actual benefit in it for them. Companies that do adopt it, like many Big Tech firms in the past few years, are also the ones that had much more generous paid PTO to begin with - at Microsoft, for example, as a senior engineer, I had four weeks of PTO before the switch.

So, you need to look at comparisons before and after UPTO adoption for the same company to see the trend. Conveniently, that very article you linked to has some sources for that, e.g.: https://www.bbc.com/worklife/article/20220520-the-smoke-and-...

There are other negative aspects to it, too. For example, when you have guaranteed vacation PTO, it is wholly separate from other things like paid medical leave. But with UPTO, it's that much harder to argue for it to your manager if you have already taken medical leave that year.