Well I enabled the default Jetways in P3D V3 since I ran the latest update, and the Jetways won't move when hitting Ctrl J. Looks like the update messed up the default Jetway action.
If you reenable default jetways, GSX is no longer affecting jetways anymore and CTRL+J will work as before. Of course, before replying, I tested both in P3DV3 and P3D4, and default jetways works just fine with CTRL+J, when re-enabled from the GSX Control Panel, see the attached screenshot.
So, the only possible explanation that your default jetway didn't move, is that jetway, with that airplane, parked in the same position, wouldn't have moved in any case, regardless of GSX.