I think the author is not taking language far enough. The animals which cannot speak do have a language, their language is just body language — one of actions. This is why when learning how to train dogs or cats, a human must learn how to control themselves and their actions.

Yes, there is not reason why AI must “speak” in English or any other human language, but any language it speaks in will be lossy in the same way. Fundamentally, all of communication is lossy including our computer programs. This is why things like undefined behavior exist and also why people misunderstand.