I think he is using misleading terminology.
Nobody offers "unlimited" PTO....that's just stupid.
What the majority of companies, especially ones that aren't service industry or retail, like real and pseudo tech companies, are moving to what is called "Open Time Off".
Originally, salaried employees would receive x number of weeks of Paid Time Off based on months/years of employment.
The problem with that is, on the books, that was considered time(money) owed to an employee and if they didn't take all the PTO allotted to them by the end of the year, it really fucked with the company's financials. Many companies tried to implement a "use it or lose it" policy, but that wouldn't always be enforceable depending on the state or country the employee was in.
So within the past 10 years, most companies have moved to an Open Time Off policy. Nobody has a "bank" of hours they draw from; if you need a day off, take a day off...if you need a week off, take a week off...if you need a month off, take a month off. But don't think we aren't watching you.
If you've been here for 2 months and now want to take a month off, don't be surprised that you don't get your raise or bonus when you thought you would.
If you've been here 5 years and want to take 6 months off for no reason, don't be surprise if there is someone else doing you job when you get back and you've been reassigned to the mail room. It's all very much an honor-system type of thing and the company has the freedom to make a "judgement call" should they feel you are abusing OTO.
I'm 99% sure that is what he is referring to.