I think the blog post is arguing against a volley that happens all in one instant, requiring all the archers to synchronize perfectly. This seems pretty easy to argue against because while movies do it because it's dramatic and cool, it's harder to justify in actual combat situations (and the post goes into great detail on the pros and cons).

However, it seems a lot more reasonable to suppose that archers were sometimes told to hold until a given strategic moment. In that case, you might see something resembling a volley when, say, an advancing enemy reaches a particular position and the archers begin loosing. But I don't think that's what the post was talking about.