I think " all prey" is relative, in that the kind of dog you are working, matters quite a bit. Prey work was introduced when the dogs were a heck of alot more serious, due to genetics and to a lesser degree, how they were trained. It was used to relieve the pressure and to channel the aggression into the bite. The dog learned they could get calmness in the bite.
I have a female who is really serious. No helper will be needing to get right on top of us to get aggression from her, that's for sure. I don't have super talented helpers but I tell the one who does know some things, to stand still, let her bark and then do nothing but prey attractions before the bite is offered. No one watching that dog has considered for one minute that she was an "all prey" dog, that's for sure. In the beginning, when she was much younger, she would bite what was offered. Amazing how some people offer their body more than the sleeve when they are in front of dogs like her but some of them did. lol.
Anyway, while not "all prey", most of it is and no matter how much a helper swings that sleeve around, she will never view the work differently. She will channel the aggression into the bite/sleeve but the helper will not be her playmate and if there is no sleeve there, she will bite him.... if he so desires.
There are now dogs who will change and it becomes all about the sleeve and not at all about the man. They are lacking the heart and courage to take a man on if you ask me. This is why some are constantly trying to pressure their dogs in order to "fix" that. Many times you can't. You can make the dog more serious but they will never view it like the female I just talked about. It is not in their genetics.
Oddly, my dog would be the kind that SchH people might think there is something "wrong" with, because she won't play with them. She means it, its the social aggression we talked about in the other thread, but is again, something most people don't understand anymore. It is active aggression that does not require big threatening actions from the helper. Once she figured out what it was about, she sees him and it's on. She doesn't need running, whip popping or someone right there with a claw shaped hand....she loads when she sees him or suspects that he is nearby.