While it is fully grade-separated, it's very short, and technically not part of the real motorway here, which would be the Airport Connector—this part of Paradise Road branches off the terminus of the Airport Connector at the series of terminal access flyovers before the tunnel. Another reason for this being primary over motorway would be it's narrow arterial road-like concrete median and low speed (35 mph), making it feel like a regular road when you drive along it instead of like a freeway as does the Connector. Part of the Airport Connector does have a low speed limit, but it retains a freeway-like structure and the speed limit increases once it exits the tunnel, whereas Paradise Road is just an arterial road that passes through an interchange partially, connecting to the other freeway at its end. Granted that it's a halfway combination between arterial road and freeway, I supplemented that with the expressway tag.