The point of these really heinous execution methods (wheel, fire...) is to wreck the victim's "honor". I think it's because you go totally batshit when you are

The point of these really heinous execution methods (wheel, fire...) is to wreck the victim's "honor". I think it's because you go totally batshit when you are being smashed up on the wheel. After a public display like that it does something to what people think of you, your associates, your religion... It mentally scars the audience. And all memory of you will be strongly associated with that scar. It's a kind of social damage. Yes, a lesson to those who might be inclined to do what you did. But also a kind of theater, recasting you as something demoniacal.