Make "urgent" case status not-reserved

The screen /civicrm/admin/options/case_status?group=case_status&reset=1&action=browse
(eg http://drupal.demo.civicrm.org/civicrm/admin/options/case_status?group=case_status&reset=1&action=browse)
states that "The existing option choices for Case Status group are listed below. You can add, edit or delete them from this screen." but in fact it is not possible to delete Case Status Options at all in Drupal 7, although it is possible (using CiviCRM 4.2) in Drupal 6. Nor is it possible to disable any of the supplied 3 case status options (Ongiong, Resolved, Urgent), as the Enabled field cannot be unchecked.
The consequence is that if, for instance, the Urgent status is not applicable then it cannot be disabled or deleted.

The functionality of the same version of CiviCRM should be the same in different versions of the CMS.

Screen-shot of the corresponding screen in a Drupal 6 environment is attached.