The problem with all this is that the Eastern churches had a long familiarity with the rival scriptures, but rejected them because they knew they were late and tendentious. Even as early as the second century, the Diatessaron assumes four, and only four, authentic Gospels. Throughout the Middle Ages, neither Nestorians nor Jacobites were under any coercion from the Roman/Byzantine Empire or church, and had they wished, they could have included in the canon any alternative Gospels or scriptures they wanted to. But instead of adding to the canon, they chose to prune.
