OLD TESTAMENT PSEUDEPIGRAPHA WATCH: The Christian Monks Who Saved Jewish History (Malka Z. Simkovich, Lehrhaus). HT Mosaic Magazine. This article deals with St. Catherine's Monastery in the Sinai and Mount Athos Monastery in Greece. Scribal monks did indeed save much ancient Jewish literature from oblivion.
That said, the examples given are mostly problematical. It is debatable whether Joseph and Aseneth is a Jewish work. The Greek Testaments of the Twelve Patriarchs, including the Testament of Levi, draw on some Jewish texts, but are Christian compositions. It is correct, however, that the Testament of Levi manuscript from Mount Athos contains (in Greek translation) some verbatim material that is otherwise only known from Aramaic Levi.
The Testament of Solomon is a Christian composition. The Testament of Adam probably is as well. It is not clear whether the Testament of Job is a Christian or Jewish composition.
There are undoubtedly Jewish texts that survive in Greek and were transmitted only by Christians. These include Greek translations of the Book of Watchers and of the Epistle of Enoch (both from 1 Enoch), the Letter of Aristeas, 3-4 Maccabees, and, as the article does mention, the works of Philo and Josephus. But I'm not sure how many of these, if any, survive in manuscripts specifically from these two monasteries.
My caveats aside, it is always good to see the Old Testament Pseudepigrapha getting some attention. Hopefully a more nuanced understanding will filter out into popular coverage in due course. And, as I said, the main point of this article does stand. For some bibliography on the topic of the provenance of such texts (by me) see the list here.
For much more on St. Catherine's Monastery and its manuscripts, start here and follow the many links. And for more on Mount Athos Monastery (and its cats!), see here.