Yes, but is there a way to change that?
Editing the AFCAD, of course.
Many AFCAD of 3rd party sceneries are not made with enough attention to ground vehicles, some are missing vehicle paths entirely, some have vehicle paths not connected correctly to the vehicle parking spots ( assuming there are some ), some have plain errors like orphaned nodes, duplicate nodes, etc.
GSX obviously tries to use vehicle paths if possible ( even if the path is longer, GSX will still try to take vehicle paths by preference ), but if there's no other way, it will take taxiways.