It is about that. You are confusing the definition of a word, versus the legal charges.
Homicide is a word that means killing of another human being.
Similarly, parricide is killing a familiar (usually your parents), or regicide, and so on and so forth.
Those are words with a meaning in the dictionary.

And then you get into the category of what kind of crime.
If you commit homicide but you're a soldier in a war, it is not a crime, but if you commit homicide, voluntarily it is a murder, but it's still homicide.

You're mixing two things.