You're right. But it seems ironic that a company would ban one of its own products. It also highlights a few challenges as cameras become even more ubiquitous and integrated with other devices. Will everyone be willing to leave their devices home or at the door? Will the rules even be enforceable? It seems like the live performances I've attended lately have given up on the "no cameras" rule.
Practical applications increase the worth of pursuing the knowledge. Including that information helps me evaluate how much the knowledge is worth.