Exactly which Jews are you referring to? There were at least five different Jewish Canons that I am aware of; The Sadducee, the Pharisee, the Essene, the Septuagint and the Babylonian, none of whom agreed. The Church accepts the Septuagint because partly because it was accepted by the largest number of first century Jews.
I think different posts are being conflated, but I think I’m asking the same question you are: Is every ancient translation ‘Septuagint’ or was there one Septuagint translated by the seventy elders? Who decides?