This reminds me of companies who have “unlimited” vacation days. If I can’t take the next 40 years off at full pay it’s not “unlimited”.

A more accurate description is probably “vacation days determined by whether your manager likes you”.

Unlimited vacation is such an obvious lie, I'm surprised so many people see it as a perk.

It's like claiming to have flat structure. Nope, there is still a hierarchy, just like there is still a limit to the "unlimited" vacation days you can take. You just took something explicit and made it implicit to the detriment of your company.

It's a red flag when I see either of these advertised as perks and it makes me less likely to work for the company.

I've turned offers down over that. I will not work for a company that claims "unlimited" vacation, unless they're at least prepared to specify a contractual floor.

I also don't like it and I believe it's not necessarily legal in all countries. Many European countries have a minimum amount of vacation days and companies need to make sure employees also take those (not all do but theres no enforcement unless someone complains). "Unlimited" without a floor might lead to more vacation days for some but likely to fewer days for most.

And if they were truly unlimited, why would anyone work part-time? You could just work full time and take 2 days off per week (plus vacations) at full salary. But I doubt many companies would accept that.

as mentioned earlier, setting boundaries is up to you

My wife's sister once said my problem was that I couldn't say no.

One of the most difficult but most empowering skills to learn, in my opinion