That scenery has SODE jetways, and they cannot be excluded like standard .BGL jetways.
GSX normally doesn't allow you to replace jetways on a scenery that already comes with SODE jetways but, if you *really* want to do it, you must remove their XML file in the C:\ProgramData\12bpilot folder. However, you must be careful doing this, because the scenery might also use SODE for other things so, instead of removing the file, you should edit it to remove just jetways. If it contains only jetways, you can just remove it.
Then, you can start customizing it with GSX jetways.