Luther does not give all books of the the Bible equal weight. He evaluates them in their gospel content. John, Galatians and Romans get high marks. James and Jude (which were not considered apostolic by Eusebius), not so much. Here is his criteria, his true test:

“Now it is the office of a true apostle to preach of the Passion and resurrection and office of Christ, and to lay the foundation for faith in him, as Christ himself says in John 15[:27], “You shall bear witness to me.” All the genuine sacred books agree in this, that all of them preach and inculcate [treiben] Christ. And that is the true test by which to judge all books, when we see whether or not they inculcate Christ. For all the Scriptures show us Christ, Romans 3[:21]; and St. Paul will know nothing but Christ, I Corinthians 2[:2]. Whatever does not teach Christ is not yet apostolic, even though St. Peter or St. Paul does the teaching. Again, whatever preaches Christ would be apostolic, even if Judas, Annas, Pilate, and Herod were doing it. But this James does nothing more than drive to the law and to its works. Besides, he throws things together so chaotically…

—Martin Luther, (LW 35:396-397)