The only difference is that I get paid out any remaining PTO, should I leave, whereas with unlimited, there was no expectation that it will be paid out on departure.
My current company recently made a rule that you have to apply for time off through the HR software. Not make it harder to take PTO—all requests are auto-approved-just so HR can track it. At the next all-hands the CEO said something like "You guys work really hard... we're, uh, worried." My manager has been bugging me to take a proper vacation instead of my usual day off here and there.
There are certainly awful, exploitative workplaces out there. But there are also great companies run by good people.
At one place I worked at, they only gave 3 weeks, but with the option to "buy" a 4th week with a slight salary reduction that effectively made that 4th week unpaid, but with the loss of pay spread out over the year. It was nice, though I actually wish I could have taken more, especially since the company did a shutdown between Christmas and New Years and forced you to burn a week of PTO at that time, which meant that you really only got 2 or 3 weeks throughout the year to do what you wanted.
More recently, someone I know who worked at a well-known unlimited PTO company told me that a newly hired head of corporate communications quit in short order because the CEO would actually go radio silence on vacation and they couldn't deal with that.