As explained, many times already, GSX can't decide automatically if the Pushback preference was set to "None", because the scenery designer really *meant* no Pushback should be allowed on that parking, or simply because he made a mistake/forgot about it.
The customization option is already there to fix this, I doubt *all* the airports you fly into all have pushback disabled but if they do, it's the AFCAD which is broken. Even default FSX airports have their pushback preference set it quite reasonably, one would expect a downloaded AFCAD would *improve* on the default one, not worsen it...
However, we are probably can deal with it, by putting a global option to just ignore an AFCAD pushback preference set to "None", and consider it as being "Both". Of course, it would be your responsibility to then choose the correct direction, because if the way you chosen put your airplane with the nose in front of a wall, it's nothing that GSX can fix.