No big deal though really, I think I'll just disable the GSX marshaller instead and rely on my own parking skills
Please note the GSX marshaller is supposed to guide you with the center of the airplane ( the red cross when you see the plane from Top-down view ) in the same position as the parking center as defined in the AFCAD, which will be the same situation you would have ended up if you selected the parking from the standard "World->Go To Airport" menu.
Whether this is appropriate for that parking, or that airplane type, is an entirely different issue, which can usually be simulated correctly only when the scenery has been designed for GSX (such as several FSDT sceneries).