Inerceptions always follow a process of escalation. You don't start an interception by going wing-to-wing (also because you don't start your interception in sovereign airspace).
Also, in this case China recognizes that land as theirs and thus that the 12 nm around it are recognized as territorial waters. Thus, it recognizes that Canada intruded on their sovereign airspace... And in that context, China would be well within their rights to shoot the plane down. From what I understand, because it's disputed between China and Japan, Canada asked Japan for permission but not China.
China has the most batshit, nonsensical territorial claims of any country on earth. They could shoot us down alright, but since everyone else on the planet would agree that it happened in international airspace, they would be really fucking stupid to do so
Except... That's not at all what people are saying. It would be either Japanese airspace or Chinese airspace. It's not China claiming an island alone. It's China and some other party contesting the claims. Only the Western powers claim it to be international airspace.