This is the offending method which will always return the configured job category even if it is not authorized to view the job templates. https://github.com/theforeman/foreman_remote_execution/blob/master/app/models/job_invocation_composer.rb#L584
This is a duplicate of BZ #1993679 or at least the fix for it seems to fix this one as well. Closing *** This bug has been marked as a duplicate of bug 1993679 ***