I doubt they will fire first. All they need to do, is for us to fire first, then they have achieved a propaganda victory similar to the Brit incident.
Nah. There, the Iranians assaulted that small British patrol with overwhelming firepower, here it is the opposite, a small Iranian patrol attempting to take on vessels far more powerful than they are.
It is a propaganda victory for them if they come away from that encounter without being obliterated.
They weren't, hence it becomes another in a string of such propaganda victories that we are handing them by fence-sitting and ham-handed rules of engagement.