Not even workers in France get a few months vacation. What are you after here?
I work at place with about 5 work weeks off, which is a lot for the US, and there’s never any question about whether you can use your time or not because the number of days is exactly specified. I like that better than a vague “unlimited” (but not actually) policy.
The policy is unlimited. You are welcome to take a year of vacation a week after you start. However, there are other factors, such as remaining employed. You most likely won't be meeting your job duties if you're on vacation for a year.
What you describe sounds a bit like "if you manage to do your work faster, you can take the remaining time off", correct?
You're expected to do your job to remain employed. You are welcome to take as much paid time off as you want, in which you would ignore your job.
Assuming you did your job well, this won't be a problem. You either set things up to run on their own in the short term, or you've sufficiently cross trained someone else who isn't on vacation to cover for you.
What I'm saying is that if you try to take a year of paid vacation a week after you start the job, it's unlikely that you've set up either of those things before you go.
No one is strictly necessary. You can bring value to the company and it still doesn't mean that the company would go bankrupt if you left for half a year.