Indeed, and one hates to curtail dialogue, but at the same time, I think part of the idea of a culture of “open by default” is to reduce the amount of dialogue and therefore the amount of time it takes to get access to information.
Canadians have dialogue all the time with government about access to information requests. Usually it's because they're not getting the information. This is one of the rare cases in which I think a reduction in dialogue is actually a sign of progress. It means Canadians and parliamentarians, in this case the parliamentary budget officer, are getting that information in the most timely way possible, which is the point of being open by default.