Exclusion means, at least in the current statute, means that it's just not available—not even for review. Whoever claims it to be an exclusion is absolute, and therein lies the flaw.
I have no assurance as a Canadian citizen that this is being done properly. I don't mean being done in bad faith, but that it is being done properly—and the courts can't review it either.
With an exemption you would apply the same sort of logic: the injury test and a series of other disclosure tests as to whether it should be disclosed or not. If it is your political function, it should be fairly obvious as compared to the cost of getting you from A to B.
I feel quite confident, even as a former parliamentary officer, that those exemptions would be more than adequate to protect the confidentiality of the politically partisan party and legislative functions.