Another downside to unlimited PTO is if the company decides to lay you off. If PTO is defined, then in California, they have to pay it to you. If it is unlimited, then there is nothing they need to pay you.
This is important. With unlimited PTO, you no longer accrue PTO hours per pay period. Those unused PTO hours are legally required to be paid out at your usual rate when you leave, regardless of reason. I'm actually surprised that this isn't mentioned in the article at all.
Which is why, when in the context of unlimited PTO, it is sometimes suspicious to take a long (2 to 3 weeks) vacation. It is a hint that you are taking advantage of the PTO before leaving.
My idea of "forcing" is statutory time off like the rest of the developed world". American businesses have proven they can't manage the time off benefit in a way which balances the needs of the employee and in the long term helps the business as well.
In America, all that matters is short term profit, not the longer term picture. MBA's fail to grok this.