Toronto's bigger. Same reason Boston and Washington are "New York" and Seatle/SanFrancisco are Los_Angeles
(Detroit gets its own zone because it was significantly different to new york before 1970, normally it's only difference post 1970 which merit a new zone)
(Detroit gets its own zone because it was significantly different to new york before 1970, normally it's only difference post 1970 which merit a new zone)