Scripts are selected for each nzb individually. The settings provide defaults; once nzb is added to queue the changing of settings will not have effect on nzb which are already in queue. When you click on nzb in queue or in history, then on button "Postprocess" here you can see selected scripts and change scripts for that nzb.
Now for a test add some nzb with other category, then click on nzb in queue and on button Postprocess. Is the script selected?