More or less this.
Personally I see growling as an expression of displeasure or annoyance. Kinda like a dog upset about someone taking his bone. Or Applejack upset about thieving varmits. Even then, I wasn't even aware we had a "growling" tag until now, I've so far used "gritted teeth" to cover this situation.
Snarl/snarling I see as a much more feral, aggressive, dangerous expression. If something is snarling at you, you better ne ready to fight for your life.
To use the images above;
Growl — Daaw, look the doggy is upset…
Snarl — Oh god, this beast is going to rip my throat out!
Is this enough to warrant two different tags? I'd argue it is, but that's just my two cents.