… in AD 382, why do the Orthodox have a different canon?
The Canon of Scripture was settled in Local Western Councils, not Ecumenical Councils until the Council of Trent. But the Council of Trullo which the Orthodox Church accepts as an Ecumenical Council, accepted all Canons of previous Councils, Local and Ecumenical. This therefore meaning that the Council of Trullo accepted the Canons of Carthage, which was one of the Local Western Councils. The Local Council of Carthage was one of the Councils that named Scriptures that are to be read in Church under the name “Divine Scripture.” This list at Carthage is the same that we have at the Council of Hippo and later the Council of Trent. The Orthodox Church, as I see it, do not read any books in Church that are outside these books listed at the Council of Carthage, ratified by the Council of Trullo. Though they do not read all the books listed from Carthage in Church, they certainly would not read any books outside that list from Carthage under the name “Divine Scripture.” So even though their Canon of the Old Testament has more books than our Canon of the Old Testament, they wouldn’t read in Church books listed outside what became known as our Old Testament Canon. I hope this makes sense. One important point to remember is that they do accept the Deuterocanonicals as Scripture, which is a historical testimony to the Early Church having great reverence to those Books.