Interesting. I can't discount your experience, because they're yours.
Typically, when I see dogs quit, they're very tired, beaten down, and not much is "standing up" on them at all, and especially not their tails.
My own experience has been "tail-up/fuzz-up," when they're still full of energy ...
I would think a dog would have to be quitting awfully early (and awfully rank) to have its tail and fuzz still standing up ...
Good analogy. I am not sure the animals are consciously trying to "look bigger" ... so much as their adrenal system kicks in. Maybe it's simply a function of the adrenal system, which causes the body to react.
I agree, it is good to analyze the signs these animals give. Even among human beings, one of the key challenges is "misperception of facial expressions"; studies show we humans can misperceive each other's signals, let alone the signals of animals.
Those with "gifts" (in dealing with either people or animals) are the ones who can read them right ...
Jack