In a nutshell you appear to be saying that the members of a sect consider the founder of the sect to be authoritative.There was a standard used to decide which writings would be accepted as canonical. Jesus wrote no books, but taught orally and by example. The followers of Jesus recognized Him as divinely authoritative long before His words were written down, much less assimilated and officially canonized by the Church. For example, the officers who refused to arrest Jesus declare, "No one ever spoke like this man" (John 7:46). Similarly, Peter proclaims that Jesus spoke the words of eternal life (John 6:68). The Church had the essence of the New Testament canon before any of the books had been penned. After they were written down and began circulating in the churches, they were considered authoritative not as holy books as such, but as writings that contained the holy words of Jesus. The authority of the words was primary.
But that did not stop people from ascribing their own ideas to Jesus then writing them into the Gospels before they were canonised.
You might find this old thread by @The Reverend Bob to be illuminating on this topic;
The Conflicting Theologies of the New Testament