Perhaps he included teachings that provided further explications on: <14 examples listed>…
which is why the Catholic Church retained these teachings, as she was able to access his words through Sacred Tradition.
Perhaps? Don’t you know? Does anyone know? Is anyone telling?
What was Paul’s contribution to “Sacred Tradition”?
All apostolic teaching that God deemed necessary for the faith and practice of the church, and for “the wisdom that leads to salvation”, was preserved in sacred writings (2 Tim. 3:15-17). It is a reasonable and logical inference that God would preserve what He inspired. But oral teachings of the apostles were not called “inspired”, except for what was recorded as Scripture.
Scripture is clear that, from the very beginning, God’s standard was that His revelations be written down and preserved for succeeding generations.
“Moses then wrote down all the words of the Lord” (Exod. 24:4), and his book was preserved in the Ark (Deut. 31:26).
“Joshua made a covenant with the people that day and made statutes and ordinances for them… which he recorded in the book of the law of God” (Josh. 24:25-26) along with Moses’ (cf. Josh. 1:7).
“Samuel next explained to the people the law of royalty and wrote it in a book … ” (1 Sam. 10:25).
Isaiah was commanded by the Lord to “take a large cylinder-seal, and inscribe on it in ordinary letters” (Isa. 8:1) and to “inscribe it in a record; that it may be in future days an eternal witness” (30:8).
Daniel had a collection of “the books” of Moses and the prophets, right down to his contemporary. Jeremiah (Dan. 9:2).
Jesus and New Testament writers used the phrase “It is written” (cf. Matt. 4:4, 7, 10) over 90 times. This testifies to the importance of the written word of God. When Jesus rebuked the Jewish leaders it was not because they did not follow the traditions but because they did not “understand the Scriptures” (Matt. 22:29).
All of this makes a strong case for God’s intention from the very beginning that His revelation be preserved in writing (Scripture), not in extrabiblical tradition. To claim that the Apostles did not write down all God’s revelation to them is to claim that they were not obedient to their prophetic commission not to subtract a word from what God revealed to them.