That's a fair point! Fortunately, our company culture plays a big role here - unless folks truly don't want to take much time off, everyone seems to take about 6 weeks off. Some teams even plan entire weeks off near holidays so that everyone gets rest and work can be planned/scheduled more easily. "Unlimited" means: assuming you get your work
done and are a reasonable team player - take all the time you need (which seems to be 6 weeks, ha)
It can be a slippery slope for sure, I think it only works when the entire team buys into the notion that life is always more important than work (which can feel rare over here).
Happy to say this has been working for me and if the attitude started to change, I like to think I would speak up pretty quickly.