>>44970779Because that pokemon in its original language it uses very old terms, for example, in ancient times in China and Japan any aquatic animal that had a shell was classified in the same way.
The same goes for mixing terms such as weasel, badger, raccoon and raccoon dog in the same kanji or the most famous is mixing the term for rat and mouse in even any similar animal such as possum and shrews in NEZUMI.
Basically they are archaisms that have lost their use. A more recent example is how the Egyptian jackal (Canis anthus lupaster) previously classified as a subspecies of the golden jackal (Canis aureus), but in current times it was shown that it is actually a wolf.