I may be wrong, but, for example: Our friend, let's say Mark, tend to eat a lot of spicy things like: chilli peppers, tabasco sauce, hot saucepans and sometimes very hot mexican soup. (I'm not good at kinds of food.) And we may say: "What things he eats!" And in this contex we say that he eats not only these things I mentioned, but also other kinds of spicy food like for example Santa Fe Chilli peppers (I've found it somewhere in the Internet, but never mind) , which are so spicy that people can't eat them. So in this case we widen the meaning of exclamatives.
As I said I may be wrong, if so, correct me, please.