Luther did not see the apochrypha as scripture just like, Jerome, Gregory the Great, Cardinal Cajetan (Luther’s Catholic Opponent), Cardinal Ximenes and a myriad of other notable Catholic Scholars.
That is precisely the point - if anyone can decide the canons for themselves, Luther included, than how do we know the actual canon? Anyone is now free to add and delete to support their own theories. If Luther has authority, than anyone has authority and then it is a free for all.
For up to 30 years after Christ’s crucifixion, no new testament was written yet, and ALL information about him was transmitted orally. So at least those Christians couldn’t say- it’s in the bible -so what did they do? (rhetorical question)
It took years for Christ’s teachings to be written down, and then several hundred years before any texts were considered official. (Council of Hippo, St. Augustine, 393, Carthage, 397).
Christians in the beginning did not have the bible alone - they depended upon oral tradition. Christ was a preacher, not a writer, and the first Christians never saw a complete bible.