If that's the case, then why does the Crown still have the "constitutional" function at all? Why doesn't the Prime Minister ask the courts to dissolve Parliament? Or open Parliament, for that matter?
The Sovereign's representative is supposed to "deny absolute power" from politicians. If the courts are "really" responsible for doing this (along with the media, and public opinion), and the Governor General is "only" a ceremonial facade, then why does the institution exist? Indeed, a recent issue of The Economist, I believe it was, suggested that a majority government in Canada is restrained by the courts and public opinion, implying that the Queen's representative has no role whatsoever.