Question: What does this author think happened instead of the volley? Does he expect that archers just started randomly firing when they felt like doing so? Of course not. They waited for the order to start firing. So the first shots would, imho, constitute a "volley" in that everyone would be launching in the same few seconds. Subsequent shots would then become less coordinated, but that first wave would be a true volley. Then orders would come to stop/move/start, resulting in other coordinated volleys.