An interesting point you raise joyey jojo, the use of the word "katholikos" as being very early. It shows that there was as early as that a group of Churches who considered themselves to be "the whole Church" and thus were dismissive of Christian groups outside of theirs as not Orthodox.
This thinking must have arisen because of the size of their group, compared to the others, who were probably dwindling in number by then, so they claimed the evident blessing of God upon their Pauline Christianity. At that time of course there was for sure no fixed "Canon" so they must have judged the other groups on difference of Doctrine and interpretation.
The same thinking pervaded the JW's in my youth : " Look how fast we are growing ! We must have Jehovah's blessing !", that thinking is still there to a degree, of course it is not only a fallacy to think that way, but the figures rather go against it too, much larger Christian Groups are also growing faster. Thanks for your thought on this.