GSX surely always reads the .INI file of the scenery.
The parking radius has a lower priority of the Max Wingspan setting so, if you change it after having specified a Max Wingspan, you can change it as big as you like, it still won't affect the decision if the parking is big enough for the airplane. This is correct, since the Max Wingspan should correctly have the highest priority over the parking radius, which will be meaningful only when NO Max Wingspan has been specified and yes, you might have good reasons to set the radius independently of the Max Wingspan, since the Max Wingspan is used ONLY to decide of the parking is suitable for the airplane, but the radius is used to place vehicles, but only if NO custom placement is used. If you place the vehicle starting positions manually, then the radius won't be used for anything.