The FS Labs controls the doors by itself by reading the GSX status so, nothing you see has anything to do with GSX.
There's an additional 2-3 minutes delay after all passengers boarded, during which you might see the GSX request to close a door, but it won't close immediately because FS Labs is simulating the dispatcher coming on board to finish the paperwork, so this is entirely intentional and, in fact, we were discussing sending this guy as animated character, so people won't assume there's some kind of "bug" in GSX, just because the airplane is waiting to close the door.
Of course, you can always increase the time between GSX messages, if the default frequency is too high for you.