That seems a little self-contradictory yourself, though. If canon can contradict itself freely, which I entirely agree with, then why would contradictions be a reason to say that something can't be classified as canon?
(I'm not claiming a position on tie-ins being put at the level of canon myself here, I'm just pointing it out.)
Because it's not about consistency. Like I said, it's just a label for the stories by the core creators as distinct from stories by other people.