This for real. Alllllllll of this. All of these sounds are the way different people speak based on their emotions. A snarl is not going GRAWR like a dog. It's so furious their teeth are bared, every syllable sharp and cutting and loud. A growl is lower, the words dangerously rough and hot, a warning.
It's the same with softer sounds. A purr is that low, gravelly mmmmm noise of pleasure, or words warm and smooth as melted chocolate. When someone chirps, it's bright and happy and quick, the syllables a little clipped in excitement. Panting is not tongue lolling like a dog; it's a heaving chest and words that are half-breath.
This is what language, what storytelling IS. It's symbolic, it's imagination, it's metaphor and analogy and simile. Strip that away and all you have is textbook descriptions, which are of course useful when reading actual textbooks, but far less entertaining when reading a goddamn fictional story.