Oh dang. I can't remember the last time I saw that on a menu.
(I know what I'm making for breakfast this weekend...)
To answer your question: I'm really not sure. From what I can tell, 'hash' is a catch-all term for a potato stir-fry in my hometown (we would call that a "southwest hash" and drop the name O'Brian, because American history is awful.) and hash browns are a specific dish of shredded potatoes cooked on a griddle.
But yeah, that's a good debate also. What is the difference between a hash and a hash brown? if any?