If you want to truth about whether Prots or Caths changed the Old Testament canon, the answer is unironically that almost everyone in the Christian world was just bullshitting for the first 1500 years. No one knew the exact boundaries.

What is consistent is that there are supposed to be 22 books, one for each Hebrew character, and Protestants are closer on that front, but the exact list is inconsistent. Origen omits the minor prophets but includes 1 Maccabees.