That's correct. As long as the exchange to which the order is routed is presenting NBBO at the time the order is executed, then the broker is compliant with Reg NMS.
Also note, if that exchange is not offering NBBO, it is bound by Reg NMS to route onward to the actual venue that has NBBO. The exchanges are also bound by Reg NMS, not just broker dealers.
Also note, if that exchange is not offering NBBO, it is bound by Reg NMS to route onward to the actual venue that has NBBO. The exchanges are also bound by Reg NMS, not just broker dealers.