The storyteller is not crafting an illusion out of physical matter. A storyteller has a word to describe that sound, and should not need to resort to snorting, banging, or growling, let alone costumes and finger puppets. What's worse is the general public has been ill educated about what good storytelling is. It is for these reasons that I have left the storytelling world and joined the poetry world. Poets are open minded, accepting, and most of all, interested in the imagery of the spoken word, not the antics of the performer.
Storytellers can be actors.
Actors are often storytellers Storytellers are often actors. I would agree that some people take it a little far into the acting realm. One thing to consider, storytelling can't be defined easily, and people are pushing the edges of the envelope all the time. I'm one teller who enjoys making strange noises, faces and more. If we can't say what it is, maybe we should hesitate on saying what it isn't.