Eh. How you think about this kinda depends on how widespread and diverse you believe non-Pokémon animals are in the Pokémon world, which is awkward because early generations and anime episodes often implied that there were quite a lot of them and then later on they were sort of quietly swept under the carpet and it’s hard to tell whether they were retconned out of existence or we just don’t care about them, and personally I kinda tend to lean towards the former, but… meh?
In any case, I don’t think the groups in which Pokémon are defined are terribly scientific – like, I actually think “able to use certain fighting techniques” is probably pretty damn close to how they actually think about it in-universe. Type, I’ve pretty well convinced myself now, has absolutely nothing to do with shared ancestry and in many cases (Flying, Ground, Normal, some others) not a whole lot to do with biology either, but is more of a descriptive framework for how a Pokémon functions in battle. Bear in mind that people have supposedly been training Pokémon for hundreds if not thousands of years. Pokémon training probably far predates any sort of scientifically rigorous approach to evolutionary biology, so the relevant terms and classifications are most likely to have utilitarian rather than analytical relevance – i.e., when you ask “is it a Pokémon?” early trainers would understand you to mean “can you battle with it?”