No, Pushback works in Left, Right OR Both. It will not work, of course (and this is clearly explained in the manual) if the scenery designer has set "NONE" in the AFCAD preference. GSX respects that preference, since it can't obviously known if the scenery designer set it on "None" with a purpose (es. too small parking to allow a pushback, or other scenery constraints) or he simply forgot about it. Which is why, is possible to set this preference with the GSX editor.
Note that, if the Pushback preference is set to "Left" or "Right", you will NOT see the GSX Pushback menu, but Pushback will start right away. This is of course intentional, it doesn't make much sense asking if you want to go Left or Right, if the preference says you can't go Both ways.
