I was parked at the gate at Munich, no jetway, and was only provided with stairs to the rear doors.
Regardless if you SEE a jetway or not, the parking is still considered to have a jetway, which is why GSX only displayed rear stairs. Most jetways, especially on default sceneries, only appear at the highest Scenery Complexity settings, that's why you probably believed the parking didn't had a jetway, but in fact it had.
And of course, this CAN be customized too, with the GSX parking customization editor (the "Parking has a jetway" option). The value already present is what GSX has detected from the scenery AFCAD, but you can override it, for the following reasons:
- Turning the "Parking has a jetway" ON when GSX detected it to be OFF, can be useful if you have a 3rd party scenery with fake static jetways that can't be detected from the AFCAD, so GSX will correctly turn off front stairs in that case.
- Turning the "Parking has a jetway" OFF when GSX detected it to be ON, can be useful if you want to use a parking that has a jetway which only displays at higher Scenery Complexity settings and, if you don't want to raise your Scenery Complexity setting for any reason (for example, low fps), GSX can treat that parking as being in the open, so it will display front stairs and a Passenger Bus.