We are talking about the text of the Bible. Therefore, one can legitimately compare the Sinaiticus with the KJV. The question can be put this way: if the Apocrypha was not in the TR (which all agree it is not), then why did the KJV translators translate the Apocrypha as well as the Bible?
Because it is literature from the biblical era that is good to know because their primary enemy at that time was Rome, and to Roman Catholic's these books are not Apocrypha but canonical since the council of Trent on April 8, 1546. One cannot battle an enemy in ignorance of the source of his doctrines. An organic connection with where you are and where you were is necessary to keep alive the meaning of the Reformation and be able to demonstrate the reasons for this change.
You should know that the term "Apocrypha" is a term that defines in its very meaning that the books it is applied to are not canonical. Calvin, Luther, and other Protestant orthodox all approached and argued against the Apocrypha on theological ground, and then turned around and recognized it on historical ground as ancient literature with literary value, especially polemical value in refuting Romanists. At this time the Reformers experienced humanism and its emphasis on the sources in their original languages as a ally against Rome, not turned back on themselves strangling the baby in the cradle, as it were, which is what autonomous critical thought does today.
This is self evidencing in their rejection of the theological doctrines that these books taught. For example, Maccabees teach both purgatory and worship of saints, Tobit teaches works of penance &c. They were rejecting all of these things on theological and then textual grounds once the Received Text was made available to them.
So when we look at Erasmus Latin Translation of the Received Text and the Latin Vulgate reading of Matthew 4:17 as "Do penance, for the kingdom of heaven is at hand;" we recognize that this translation is actually hermeneutically influenced by the teaching of Maccabees & Tobit. And from this arose the treasuries of merit and indulgences. Erasmus argued that the correct translation was independent of this influence and was "Repent, for the kingdom of heaven is at hand." Of course, Martin Luther picks this up and the very first of his 95 Theses is:
“Our Lord and Master Jesus Christ, when He said “Poenitentiam agite”, willed that the whole life of believers should be repentance.”
But it doesn't make a lot of sense to most people without understanding the textual, exegetical, hermeneutical, and canonical issues all synergistically coming together with the publication of Erasmus' New Testament in both Latin and Greek. But any good Protestant at this time would want to have the Apocrapha available to him to be able to show a Romanist why 2 Maccabees 12:43 has no connection to Matthew 4:17 and the Latin Vulgate is in error because the greek word is "Repent", not "Do Penance."
Why is that so much more noble or biblical than translators of the CT today when they do *not* translate the Apocrypha, even though some of those books are included in Sinaiticus. My point here is that one cannot use the mere fact of the Apocrypha being in Sinaiticus to discredit that manuscript.
Because the New Testament is a continuation of the Old Testament and must be held in continuity. The Byzantine textual tradition of the New Testament was received with the Masoretic Hebrew which has never been coupled to the greek Apocrypha, that is a unique insertion derived from the philosophical schools of Alexandria. To the Protestant orthodox the mythology surrounding an "inspired" translation of the Old Testament into greek is the foundational error which led to the mythology surrounding an "inspired" translation into Latin. Hence, the theological errors of the Roman Catholic Church has textual, exegetical, hermeneutical, and canonical issues all synergistically coming together in the Latin Vulgate.
The problem is that the critical schools are attempting to straddle a fence that cannot be straddled. To hold that the Alexandrian codices are the "most reliable" yet dismiss the canonical standing of Apocraphyl books can only be done on Reformed Protestant grounds which can only be done by rejecting that Alexandrian textual base on
theological, not historical, grounds.
Yet, the critical schools you hold to emphatically hold that these are the best and most reliable texts on explicitly non-theological historical grounds. If you are going to hold to that, then you must consider the theological validity of the Apocrapha as canonical, for on what other grounds can one reject entire books from the "best and most reliable manuscripts?" If you are going to hold that they are the best and most reliable manuscripts on theological grounds, then on what basis do you support eliminating thousands of explicitly orthodox and theologically consistent readings from the Received Text tradition while claiming their rejection does not affect any central doctrine?
To hold that these Alexandrian greek new testament texts have not been influenced by the body in which they are found is explicitly refuted in the translation of them into the Latin Vulgate, which clearly indicates their continuity. How do you know, then, that these rescensions are not a result of creating theological continuity with the greek Old Testament in which they are found? What are your older proof texts whereby you can have epistemological certainty? John Owen showed that many of the greek Old Testament readings are in fact taken from the New Testament, not the other way around.
Just as you are comparing the Sinaiticus to the Authorized Version and rejecting it, so did the Reformers and Protestant orthodox compare the Received Text to the Latin Vulgate and rejected it and necessarily the Alexandrian texts it is based upon. The difference is that the critical schools are claiming to be neutral in their rejection based upon hypothetical texts they create in their own imagination to claim epistemological certainty, while the Protestants claimed to be explicitly theological in theirs receiving a greek textual tradition in actual use for centuries by faith.