A lot of restaurant entrees (and appetizers) contain far more calories than you would imagine. Even a salad, or a piece of meat with potatoes, could easily contain 1000+ calories because of all the hidden butter and oils.
So while I understand your point about the burger in particular (it clearly represents excess), you should know that whenever you go to a restaurant it isn't that unlikely that a single course contains 1000+ calories.
I'm well aware, which is precisely my point. Most of the "normal" dishes at Disney, and many restaurants, are already pretty excessive. So to intentionally add another 300-500 calories and 20 grams of fat to a dish that was already excessive....!!!!!!