It is from Tradition/tradition…
catholicbridge.com/catholic/orthodox/why_orthodox_bible_is_different_from_catholic.php
So, at both the councils of Hippo (393) and at Carthage (397), the North African bishops worked out the final canon of the both the Old and New Testaments for the universal Church. This is the present canon of the Catholic Church, which the North Africans then submitted to Rome for final ratification. Now, we’re not sure when this final ratification was given, but we do know that, by A.D. 405, Pope St. Innocent I was promoting the so-called “canon of Carthage” (397) throughout the Western Church. Rome would also have sent rescripts of its decison (final ratification of the Carthaginian canon) to Alexandria, the 2nd See of the universal Church and the primate in the East, with the expectation that Alexandria (as Eastern primate)would disseminate it throughout the East.
Now, this was modified somewhat when, at both the Byzantine Council of Trullo (692) and the Ecumenical Council of Nicaea II (787), both the church of Constantinople and the church of Antioch (along with Rome and Alexandria) recognized the binding canons of the Council of Carthage (397). This of course included the Carthaginian Biblical canon, which is thus TECHNICALLY binding on the modern Eastern Orthodox Church.

Yet, in terms of practice, the Antiochian (and thus Byzantine) parts of the Eastern Orthodox Church continued to use pre-Carthaginian books in their local canons …and for the simple reason that these books (e.g. 3 & 4 Maccabees or the apocryphal Esdras, etc.) were always read in the church of Antioch. The fact that the council of Carthage excludedthese books (because they contain some problematic material) was ignored. And it’s because of this neglect of the Carthaginian canon (as authorized by both Trullo and Nicaea II) that modern Eastern Orthodoxy (coming out of the Antiochian Liturgical tradition) often include such books in their published canons today. Yet, technically, they SHOULD consider themselves bound by Trullo’s and Nicaea II’s authorization of Carthage.