I can also confirm that passengers do not seem to be working for the PMDG 777-200ER. Yes I have read the manual. Every time I do a livery install I open it up, uncheck the 200ER and recheck it.
But like Peter M has said, the texture.cfg isn't edited by the GSX Installer Config menu at all. NONE of the liveries for my PMDG 777-200ER have an edited texture.cfg. It is as if the installer isn't even detecting that the liveries exist. Not only does it not edit the texture.cfg, but it also does not edit the files in the model folder. As in, GSX doesn't copy (for RR specifically) the PMDG772ER_RR_EX.xml to the model folder of the livery and add all the flag files such as model.gsx, xml_copied_by_gsx, xml_modified_by_gsx, obviously because it isn't doing that.
I just installed a 777-200ER livery and MANUALLY made the edits to both the texture.cfg and the model.cfg (including airline specific crew textures) and will let you guys know if it works.
Honestly its a bit frustrating there are so many of us obviously having the same issue and the only response we get is "read the manual" like we haven't done everything correctly. I wish they would take this seriously.