At the top of the "completion_criteria_activity.php" file, I notice the following comments:
* @copyright 2009 Catalyst IT Ltd
* @author Aaron Barnes
This indicates that this report was created 10 years ago, when perhaps completion criteria were not as sophisticated as they are now. Therefore, I would say that this report, and possibly other scripts of that provide the completion criteria functionality, are in need of some modernization to make them aware of custom completion criteria.