This doesn't have anything to do with the update. If you only have a straight pushback, it means the scenery you use has the pushback specified to "None" by the original developer.
Since GSX cannot say if this was an oversight, or it was made intentionally, it trusts the AFCAD and doesn't give Left/Right, but of course you can customize this in the parking customization dialog in GSX.
With previous versions, you wouldn't had ANY pushback there if you didn't customize the parking position with a preference other than "None", now you have at least the straight pushback.