It has to do with reliability.
*Reliability" is an excellent starting off point - and really goes to the heart and soul of the very first post - the time line! You see, here the OP gave an unbroken chain for the first 100 years after Christ’s death. No political confusons by Constintine, no grave error by gnostics and no mischief by misguidedf Manichæans! This time line is nothing if it has not presented RELIABILITY in a very clear and understandable format!
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Consider these questions:
a) Can we say with great confidence (wrt 1 Cor, for example) that, “Here is what a letter, written by Paul, in the mid-first century actually looked like with only a relatively few uncertain words and phrases”?
*Is THAT what is really important, Radical? Think about it: isn’t the idea that God’s inspired Word - written in the words of men - has come down through the centuries to us - the way HE intended it to come to us? Isn’t that what is really important? From time to time I have thoughts of Paul being unable to pick up a pen … but, having a scribe write down the dictation Paul was giving! Would that change the character of 1st or even 2nd Cor? I don’t think so.
I am not entirely sure what your real argument is about this - because it was the Catholic Church you actually gave you the bible, your abridged version is based upon…

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b) Can we say with great confidence (wrt the Catholic Marian doctrines, for example) that, “Here is what the apostles actually taught word for word, about Mary in the mid-first century by way of oral tradition, with only a relatively few uncertain words and phrases”?
*Is this your argument, Radical?
Just what is it that you doubt God has done for His Own Mother? Seriously? The Immaculate Conception? (even though Paul says ALL HAVE SINNED?) Virgin Birth? Assumption into Heaven? Just because something does not exist in the Bible does not mean it is not REAL or SPIRITUAL or DIRECTLY FROM GOD! How do I know that? Simple: Matt 16 - Christ gives Peter the power to bind and lose on heaven and earth. Please note there are no limitations given. Then take John 16:19 where Christ says, “I have many things to tell you but you can not bear them now.” No where is it recorded that Christ said, “You can now bear what I am about to tell you” - and He starts to enumerate these obviously difficult items. No, you can not simply dismiss Oral Tradition because it is not writtend down…

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We can answer “yes” to question (a) and have that great confidence b/c of the wealth of manuscripts that we possess and quotations from the ECFs and based on our ability to compare and analyze them. We can therefore say that 1 Cor reliably reflects apostolic teaching w/o needing to make the same sort of faith assumptions as required for (b). The only way you can answer “yes” to (b) with similar confidence is to assume that if the doctrine shows up later in the historical record, then it must have been continuously (but only orally?) taught from the beginning…and that seems to be continguent on those faith based assumptions.
*If the bottom line is confidence based on reliability - well, may I suggest you go back to the First Post on this thread and check it out. Note, it does not start off in 1517 with the 95 Thesis being tacked to a door. You have the 1st 100 years of Christianity to look at - and marvel. If you have not gotten to the marveling part, that’s OK…

just look at what was presented from those who were closest to Christ.
God bless