Late last year my company switched to "unlimited PTO." Ironically this happened just before I had saved up 120 hours (specifically vacation hours separate from sick days or anything else) to go visit my fiance abroad without question. A couple weeks ago HR sent out a message to the managers that "unlimited" (which includes sick days, bereavement, etc) basically means 25 days at max, but we should "encourage" around 15 days.
When I brought up that "Unlimited PTO" was gonna be real bad news for us, my coworkers didn't really believe it, but now some of them are getting pushback or outright denied on trips they had planned last year. If you are applying for a company that says "unlimited PTO" ask exactly what that means. And if they say "manager's discretion" ask what the HR recommendation or policy is to the manager. It's meant to be a profit-increasing tool to get new recruits to sign on, as well as ensuring that they can cut you off from taking days off when they feel like.