Honestly, this is a no brainer since the first several hundred years of Christianity there was no NT canon at all. Though there were many writings that were shared and read in the gatherings, the list of 26 had not yet been formally declared.
Then, of course, there was no printing press for hundreds of years after the death of Christ so individuals rarely had a copy of the full text of Scripture for their own private reading.
There is no EXTRA teaching in Catholicism, just truths that some reject.
Like SELLING indulgences?