For the record, western hognose snakes can and DO display like the easterns. I've had a western hognose for two years now and last fall I was cleaning her cage when, for no apparent reason, she did the full-blown "leave me alone - I'm dead" display, complete with a drop or two of blood oozing from her mouth. I watched her for quite a long while, and after about ten minutes she started moving her mouth and "drinking" the blood back into her mouth (waste not, want not) as she turned herself over and crawled back to her hide box. It was so cool to observe this beautifully complex behavior that is definitely instinctual, and evidently adaptive!
By the way, I handle her more frequently now and she has not freaked out or displayed since the one time last fall. But I still feel fortunate to have observed the whole display so up-close and personal . . .
Tom