A320 gravity gear extension
 

When performing an emergency gravity gear extension on the A320 , you loose also the nose wheel steering . I do not understand why this happens . The gravity gear extension isolates green hydraulic pressure from the gear system . The nose wheel steering is a yellow pressure system function .
How does one affect the other ?

Ok I spotted the umbiguity : I was reading the QRH gravity extension procedure of a specific registration whose NWS is provided by the green system ( older model ) . The newer airbuses have their NWS provided by the yellow system