Where do you get that from? There is evidence in the Bible itself indicating that the Apostles used the Septuagint (See my previous post to you*). Whose canon of the Old Testament do you trust, the canon of the Apostles or the canon of a Jewish Council that rejected the canonicity of the New Testament?
*In Acts 7:14 St. Stephen says that Jacob came to Joseph with 75 people. The Masoretic Hebrew version of Gen. 46:27 says “70,” while the Septuagint’s says “75,” the number Stephen used. Following the Apostles’ example, Stephen clearly used the Septuagint.
I don't see this as being a problem. Show me one quote from any of the Apacryphal books used by an Apostle anywhere in the NT. It's a large leap of logic to say because they quoted the Septuagint in one place that they gave all the book contained therin blanket admonition as official OT. OT Conon are those books written by a prophet or during the time of a prophet. It's a simple concept really.