They weren't particularly detailed, but I did know the space quite well. I was a heavy user of other products of that type, and knew very well what I wanted out of one.
The problem is that your case is extremely rare. Most people work on systems that they never would use themselves or even know existed if not for working on it.
Wherever I work, I try to turn the system into something I would use myself. I am not always successful in this, but it drives a lot of my UX decisions, and it seems to work fairly well.