Agreed, the existence or importance of the council is largely a figment of Protestant desire to establish a legitimacy for the exclusion of the Deuterocanonicals.
What we do know is that Jewish authorities specifically rejected the Gospels as new revelation and with them the books of the Deutercanonicals.
Peace be with you
Yavneh became important when Yochanan ben Zakkai received Roman permission to establish a Jewish religious school there, and it became home to what would have been the Sanhedrin had the Temple remained.
Claiming textual variants meant variant canons is like claiming the JPS translation of the Bible, or the Soncino Chumash, is authoritative.
Jewish canon had been closed for several generations at least by this time, so much so that teachings of the school became sharply differentiated as the Mishnah. No one would have dared change the established books except to correct obvious textual errors in specific copies.
Interesting point: The late Book of Daniel was not considered a book in ‘Prophets’, but is instead included in the ‘Writings’.