Fear bitters bite with more of a frontal type snap and actually do the ripping damage. A true fight bite in defence drive, like you would see on a good Schutzhund dog on a sleeve, involves a full grip and hold until told by their handler to release.

One reliable method to read a dog is if the hair is standing up on their back -- you're looking at fear--- not confidence and that would concern me in one of the working protection breeds.