So let me ask you this;
Why would Oda make a dragon category for zoans and then make a mythical dragon fruit but not put it in the dragon category? It’s super contrived to state otherwise. If Kaido was a dragon, he wouldn’t be in the fish category of zoans.
Because the words are different.
The word for Dinosaur is different from the word for WESTERN Dragon which is different from the word for EASTERN dragon.
The word Dragon to describe th punk hazard dragon ia different from tell word Dragon to describe Kaido and momo.
They look the same in English but are different in Japanese.
So Oda is gong above and beyond with the classifications. To separate the punk hazard dragons from Kaido and momo, the words are taken into consideration
The punk hazard dragon is a WESTERN dragon which is the same word used to describe Drake. It's WESTERN DRAGON WESTERN DRAGON fruit. Then the word for EASTERN Dragon for momo and Kaido is different.
So the alternative would be WESTERN DRAGON WESTERN DRAGON MYTHICAL EASTERN DRAGON MODEL. That's what the term would look like on Japanese. And as you can see, that'a redundant as fuck.
So now we have EASTERN DRAGON separated by the mythological origin from fish. FISH FISH MYTHICAL EASTERN DRAGON (Long) MODEL
And as an added bonus a Part of Dinosaur in Japanese sounds like WESTERN DRAGON so we have a name for Dinosaur fruits
I'm telling you the names are just references to how complex the Japanese language is.