The situation you describe does happen. However, it is not necessarily the rule. Since the amendments under the Federal Accountability Act, the head of the institution has a duty to assist. If the requester asks for information and the request is not clear enough, there is a duty to assist the requester in finding the document or clarifying the request so that information can be provided within the timelines set out in the act.
So the duty to assist has been added to the act. There is supposed to be a dialogue. Some requesters ask for all the emails between the Minister of the Environment and the deputy minister of the Environment with all their provincial colleagues between 2004 and 2007.
Is the requester looking for something specific? In some cases, if requesters are prepared to be a little more specific, they will get faster service. In other cases, it will take much longer, depending on the scope of the request.