As explained many times already (too many times to count, really, there's even a blue highlight on the manual), GSX doesn't control, doesn't affect, doesn't change, is not affected by, anything related to jetways.
They continue to work (or not) as they always did. Installing GSX won't change anything about how jetways operate. Nothing in GSX can change anything related to jetways in any scenery, they are entirely and totally separate.
If a scenery developer made proper animated jetways for FSX, they would work just as they did before installing GSX, obviously because GSX doesn't affect them, at all, you will still have to operate them.
If a scenery developer doesn't offer animated jetways for FSX, GSX won't change this either.