I think sometimes something can be a bay of the Lake but not part of the Lake. I wouldn't call Chesapeake Bay part of the Atlantic Ocean, even though they're adjacent and share many of the same properties. Simply from aerial imagery, the waters look significantly different. I doubt someone in Glen Haven would say "I live on Lake Ontario". Wikipedia just calls this a "large body of water" that "flows into Lake Ontario at its northern end". I'd want to see a source that shows this bay is culturally or hydrologically considered part of Lake Ontario.