You had unlimited vacation, but you still had to get your job done.
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?
