Remember how not believing in a god is different than believing a god doesn’t exist? The same could be said about unalive. It doesn’t mean dead. It means not alive - like a rock.
Personally, I like having words that sort of mean the same thing because you can add a bit of nuance to your communication. It also makes things more interesting - a bit of variety. It’s just we have to be careful to say what we mean. It is easy to mislead by choosing certain words over others.