It would be best to continue the conversation at the Trudeau article but I think the issue that youre going to run up against is that Wikipedia doesnt exactly take the Liberal Party of Canada constitution as the Holy Scriptures  What Wikipedia cares about is what reliable sources say and virtually every reliable source has not recognized some sort of gaping vacancy in the leadership of the party for the past few years  Ignoring even common usage for a minute though even the Liberal Partys constitution itself says The person appointed as the Interim Leader may exercise all the powers of the Leader under this Constitution until a new Leader is elected by the members of the Party  I dont see anything there explicitly calling the interim leader some sort of separate office  So for all intents and purposes an interim leader is still the leader even if they were selected differently  In any event Id encourage you to make your case at the talk page for the Trudeau article  If consensus agrees with your interpretation well go in that direction