I listened to or read (don't recall which) the first book or two of that series. I don't remember that - must be later on.It's fiction. The author creates the fictional world and the rules that apply. As long as the rules remain consistent in the fictional universe, it works.
One of my favorite book series, Monster Hunter International, has a scene with zombie bears with thick metal helmets. So yeah, what you're saying is crazy has already happened.