I don't know about what they must do, but below clearly suggests otherwise.
"Parity requires that orders from floor brokers, the designated market maker, and the top of the electronic limit order book trade together. That is, floor trading interests can trade ahead of equally priced, previously arriving orders in the limit order book."
"Parity requires that orders from floor brokers, the designated market maker, and the top of the electronic limit order book trade together. That is, floor trading interests can trade ahead of equally priced, previously arriving orders in the limit order book."