That is in English... and the translators are stupid. There is no unique word for dinosaur in Japanese, so they call it kyōryū (恐竜) fear/fearful dragon. They call the western dragon too as Ryu but with the same character they use for dinosaurs, ryu basically being a group of dinosaurs which has different types. But the Ryu which they use for Kaido or eastern dragon is 龍. They are different. It was stupid of translators to make it dragon dragon because that only makes sense in Japanese to their audience.