Harmanuetics has been a long accepted rule that everything in the Bible must harmonize with everything else in the Bible.
Otherwise you have what I call shopping cart theology, a favorite of non-literalists. Take what you want from the Bible, make it say what you want and ignore the rest.
So yes, it is stated specifically for the book of Revelation, but I see no reason it does not harmonize with the rest of the Bible.
As well, well before the fifth century, the true Church had already accepted the books of the Bible we use today and rejected all the rest.
So-called church fathers, meaning the founders of the Catholic Church, recognized This reality but still added the books of the Apocrypha and some others.
So calling this argument moot, to me, is a nonstarter.