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.