Edit: I'm referring to the US with my comment
Obviously, if there is a minimum and rule that that minimum accrues if not used, it doesn't eliminate that, but it would avoid having an allotment above the legal minimum that accrues.
Obviously, though, it works best in places like the US that have no minimum (though the benefit is mitigated in those US states that don't even require paying out accrued time off in all cases to start with; the sweet spot for maximum employer advantage compared to alternatives from an unlimited PTO policy is situations like US states that do require paying out accrued vacation at the end of employment.)
Is this legally required? I worked at one place where this was the case and I was paid out for unused time upon leaving, but at another I was told I’d have to use it all up or lose it.
It’s also worth noting that employers are required to pay final wages — including unused PTO — within 72-hours of your final final shift.
So, the power move in response to such an employer would be to say you are quitting effective immediately and you expect your final check, including unused PTO, to be mailed out within 72-hours.
“Fuck me? No, fuck you.”