>Your manager can basically just allow you to be paid for time when you aren't working at his discretion

This has nothing to do with unlimited PTO, or even legally mandated vacation time. Even in Europe, which I'm sure all the people here will point to, has similar rules, e.g:

https://www.howtogermany.com/pages/employee-rights.html

>Employees must apply for vacation time and the employer must approve the written request. An employer can turn down a request due to urgent operational reasons or vacation applications of other employees who, due to "social factors", have a higher priority.