Well, its considered canon because it was added to episode IV. Anything in the movies are indeed canon. According to the article they are now considering Clone Wars and Rebels canon too. Why don't they just make the Droids and Ewoks cartoons Canon too and the holiday special while they're at it. To me only what is in the 6 movies should be canon. Really the only thing canon about the outrider is its basic shape. The interior, the pilot and any specific details are alleged. Unless they add it to rebels or the upcoming movies. What is revealed is that the ship you can barely see in mos eisly is named the Outrider. But don't get me wrong its kind of a big deal, The Outrider does "exist" in canonical terms. Before you could only assume or say its a ship the same model as the Outrider.