Doug (who can jump in with his own thoughts) may be referring to the fact that the Revelation to John is an apocalypse of the Jewish genre, and the individuals addressed by Christ are called "Jews" in contrast with their enemies who also go by the same term. (Revelation 3.9) While there is a bit of evidence that some Gentile Christians also wanted to go by the term "Jew," the metaphors, symbolism, and terminology are very Jewish. Many scholars see this as an argument in favor of a Jewish apocalypse composed by Jewish Christians.
If that is the case, "Babylon the Great" is unfaithful Jerusalem that rejected Jesus of Nazareth instead of "Rome," the other favored interpretation by those who see this as a Gentile Christian composition. The author, in this case, is making a "prophecy" of its assured rejection. This hermeneutic view makes Revelation highly anti-Semitic which could explain its late introduction into the canon. The Apocalypse of Peter instead was widely read in Christian Liturgy until the 4th century, and John's apocalypse remained challenged until the Council of Trent.
There is a third view that it is a mixture of Jewish and Gentile authorship, heavily influenced by Jewish Christian thought and written as a Jewish apocalypse, with both Jerusalem and Rome being spoken of in its judgments.
Jewish authorship, however, would not have necessarily meant the authors were from St. James' congregation. It appears that most of not all the Jewish Christians who engaged in writing were of the Diaspora or not in Jerusalem during composition, except for maybe the epistle of James.