I read it before "its just for humans" but i have seen my two (when there were two left) make syllables at each other too and not for fighting ... maybe it depends on how advanced they get
https://www.livescience.com/why-cats-meow.html
i DO understand however , other than the bodylanguage they all share that he has a variety of sounds which also vary in volume and length and tone depending on whats being communicated and that seems to be just me
indeed