You make a good point and I agree mostly to the point being made i.e. it is more fluid than categorical. However, I think it is not being made in good faith. I found the article highly insightful because it provides a solid starting point to those that have not started or don't know much about negotiations and how they happen. It should be safe to assume that there are plenty that have not started yet. It is also true that the more frameworks one reads and learns about, the more they realize that there are gaps in each one of them, and it is indeed fluid, not categorical, and hence reaching the same conclusion.