I don't think the article is arguing there would not be a starting point to archer fire. One would expect commanders to make some decision about when their forces would engage, and even without explicit command most soldiers would probably recognize the same point as being ideal to start firing. It might not be as sharp as a line of muskets, but odds are everyone would have shot an arrow before anyone got off their second.

But volleys imply a specific coordinated cadence. If you're just telling your troops to open fire, whether it be with bows or fire arms, that's not a volley.