I don't think it's all of them, but some dogs in that breed-group are like that. Our Aussie mix, Willow, is; though she's grown a somewhat thicker skin with age (she's 10). Maybe since nothing that raised it's voice has eaten her yet? She was also afraid of the dwarf rabbit I briefly fostered; it *stamped* at her. This was so terrifying that she had to hide on the bed, under the covers.

Oddly, she herself is *fierce* and *loud* when someone she does not know(or does not like) is at the door. This I attribute to her being most probably mixed with german shepherd, and territorial.