I won’t pretend to know the technical details (as the other replies do) but I want to make a point for the “pedagogical” effect here, which I agree with the author. The way I interpret the article, it’s not supposed to be a deep, theoretical treatise on the subject; more of an introductory, “intuitive” take on it. This works for those who need to either learn the concept to begin with, or refresh their memories if they don’t work with it every day. I think it’s a given that any intuitive take on a mathematical concept will always oversimplify things, with the underlying assumption that, if you actually need to know more, you’re going to have to dive deeper somewhere else. The most important thing I think is to help the reader build a rough conceptual understanding of the concept such that they can reason about it, instead of simply memorizing the terms.