Yes, exactly.
There are wide ranges of history that are still restricted. I broadly categorize those as intelligence, security, international affairs and defence. Essentially, it's any of those areas of history that are affected by section 15 of the Access to Information Act, which allows for exemptions for anything that could be harmful to Canadian international affairs, defence and so on.
A very wide range of historical matters remain restricted, including events in most of the Cold War and since the Cold War. There are many other diplomatic issues and so on for which it's much more difficult to get records.