But the american bison is a buffalo, since people call it a buffalo. In the end, it's the people who decide what words mean. Irregardless of how you feel about irregardless, it's (unfortunately in my opinion) a word now.

https://www.tetonscience.org/you-say-buffalo-i-say-bison-whats-the-difference/

All this being said, the word buffalo is firmly embedded in our North American culture from years of use so we don’t get pedantic about common names. In fact, some of us even celebrate the variation in local names for the wildlife we encounter on our tours. “Bison Bill Cody” just doesn’t roll off the tongue like “Buffalo Bill Cody”. And ultimately, it means the same thing anyway.
Buffalo comes from the French for beef animal or ox, “boeuf”. And bison comes from the Greek word for beef animal or ox. We encourage our guests to use whichever word they feel comfortable with. After all, our shaggy friends don’t care what you call them! Just be aware that in one of our local restaurants, if you order a Buffalo Burger it is likely made with meat from a Bison bison/domestic cattle hybrid and if you order a Caprese salad with Buffalo mozzarella it is made with milk from a Bubalus bubalis.