Sure in a lot of cases, growling can be a sign of weak nerves, I do not dispute that at all.. But as you say, I have too seen dogs with very strong fight and nerves growling, when engaging. I feel sometimes it helps them build up their intensity when fighting in defence.. And there is nothing wrong with a dog that is strong in defence.
I have even seen a dog in prey catch its prey and growl while shaking it.. I don't consider this a weak nerved dog either. Some dogs are just more vocal..Not unlike humans
