That's not how it works in countries with modern labor laws. You will have a baseline amount of vacation days as per the law, and employers can't circumvent that by putting "infinite" on your employment contract.
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.)