Since Christians are not Jewish it seems completely irrelevant what is or is not included in a Tanakh. Christians do not worry too much about what is or is not included in Islamic lists of holy books. Nor what is or is not included in Hindu or Buddhist lists. Christians made their own list in the early centuries of our common era and that is what matters for Christians.
No, it's completely relevant.
The OT Bible is the testimony of the Jews. They went through a long way to canonize it. It's once strictly guarded by the Jewish authority, and only authorized scribes and copy/publish legitimate Scripture to distribute to the Hebrew speaking Jews. The other 7 books are basically from the uncontrolled Greek version of the Bible. They are compiled by Jewish scholars or rabbis not as the authorized Bible but translated the Jewish religious documents for non-Hebrew speakers to have a read.
Early churches are quite isolated from the Jewish authority partly because such an authority is almost fully destroyed in the AD 70 siege (and other unrests around the period) and partly because even in the presence of such an Jewish authority they choose to reject Jesus Christ.
As a result, early Catholic churches based on the LXX to re-define the OT Canon, which is improper. God on the other hand corrected this by authenticated the Protestants.
So right now,
The Jews have the correct OT Canon, as it's their testimony and their canonization through the way from King Hezekiah till Ezra and till the Pharisees in Jesus' days.
The Catholics have the correct NT Canon, as it's the testimony of the Apostles with its canonization belonging to Christians instead of the Jews.
Only the fully authorized Protestants now have both a correct OT Canon and an NT Canon.
The trend is, when the Jews failed to to their job God shifted the authentication from the Jews to Christians. Similarly when the Catholics went corrupt and failed to do their job God shifted the authentication to the Protestants.
Thank God that we now have a half and half Catholics and Protestants in this world. Without the reformation, Christians may go wild when leaving the corrupt Catholics.
