To add to that: it also can't be "banked" (and thereby paid out after departure). Companies give free PTO because real "paid time off" has to be tracked as a liability on their books; if you haven't "earned" anything and they don't "credit" you, you aren't "owed" you anything when you leave/are terminated.

What does PTO mean here?

Personal time off (or maybe sometimes paid time off)

It should be called unknown vacation. There’s a limit, you just don’t know where it is.

I assume if you took the UK legal minimum of 5.6 weeks for example, you would get fired.

It is unlimited if the employee is talented and good at advocating for themselves.

It isn't if they are meek or mid.

In general: it's good to let your employer know that you value your time. If you don't suck, they'll respect you more, not less.

I’ve experienced unlimited PTO myself and have yet to see any kind of pressure. YMMV obviously but it’s not as universal as people say it is.

As have I. When I told my manager I wanted to use my unlimited paid time off to work half-days for the rest of the year ... the look I got was my answer. No.

Have you tried making reasonable requests though and were they denied as well?

Where I work we call it "minimum vacation", so you're required to take at least that number of days off, but you can request as much as you like over that.