edX staff users in FAP do not see the Users data (partner PC and course editors) because they are not part of the org via group permissions. This is happening because the publisher organizations/users and organization/roles APIs are returning a 403 response for this case.
Sample URLs hitting the 403 vs. a valid response when the staff user's group permissions for the org are toggled:
We should update the permissions on those endpoints to allow staff users to allow fetching this data.
Staff users who can load a course edit page can view the Project Coordinator and view/edit the Course Editors in the sidebar