After flipping through the AMM for a while I see no reason why the manual extension door with its associated solenoid controlling the bypass valve prevents operation of the nose wheel steering. It only redirects up pressure to the return lines to permit manual extension with the gear lever in any position (unlike on the older 737s).
The manual extension system supplies electrical signals to a
solenoid valve in the selector valve. The solenoid valve controls
hydraulic pressure to a pressure operated bypass valve. When
the bypass valve is in the bypass position, landing gear up
pressure is ported around the slide valve to return. This
prevents a hydraulic lock in the landing gear system if the slide
valve jams.
However, if you leave the gear lever in Off or Up, then you will indeed not have nose wheel steering, but as you know that is in the checklist.