The reason why GSX never, ever, try to start automatically, was to allow you to use it in combination with other similar services, some you might have paid for, like AES with paid airport customization credits.
Since AES always started automatically on a parking, we made GSX always starting manually, to place nice with it, otherwise they would surely conflict, since they would both start automatically. We were promised by AES authors they would look into adding a feature to prevent AES from starting automatically, but this never happened, but then AES (not being updated anymore for P3D), basically disappeared so, possibly, we might look into adding this feature with a future update.
But it will be optional in any case.