I am on page 6, point 4.2.2. The paragraph continues this way:
...interviewing every recipient of the report would have required considerably greater resources and much more time than were available for the investigation. In the interests of conducting the investigation in a thorough yet timely and cost-effective manner, the Director, Security Operations, PCO, concluded that a comprehensive examination of electronic transmissions and telecommunications involving all report recipients within the Government of Canada constituted an efficient filtering mechanism.
So in order to save time, you did not investigate all of the recipients.