Catholics misunderstand/ incorrectly teach scripture. Happens all the time. Luckily, we have an authority structure (however cumbersome) that can settle a scripture interpretation question for us if we seek the truth. Sometimes they even say “I don’t know, interpret it however you want as long as it doesn’t contradict any Church teachings concerning faith and morals”.
Ask them to show you where the bible says so. They can’t do it!!! Then you show them where the Bible says they did know they were writing the Bible.
Scripture, understood in context, cannot contradict itself.
“Tradition” in ths sense means that we look back at how scripture was interpreted by generations past.
It could be that the writers of the new testament knew they were part of a living Church that would settle the matter when the Holy Spirit moved Her to.