So is the Catholic Church, and the vast majority of Protestant Churches -- eastern, Coptic, and Armenian orthodox Churches are likewise all "Catholic". "Orthodox" just means "right believing", and "Catholic" means universal. They're not statements of doctrine or affiliation, and are claimed as titles by pretty much any reasonably large Church you can think of. In terms of doctrine, affiliation, and organization, "Oriental Orthodox" Churches are extremely distinct from "Eastern Orthodox" Churches, and in fact far more so than the latter are distinct from the "Catholic" Church, especially in regards to doctrine -- indeed, the Chalcedonian-Monophysite Schism happened over 500 years before the Catholic-Orthodox Schism was finalized.