I made this cornbread recipe from Mark Bittman. It calls for heating the fat (butter/olive oil/lard/bacon drippings) in the baking pan and then pouring the cornbread batter in. It came out great. I used butter – and less sugar than was called for, and could have used even less because of the sweetness of the corn. I wondering about this technique. It seemed to be "frying" the cornbread around the sides, which turned a lovely light brown. Is the idea that the fat gets absorbed on the outside edges only? I've made corn muffins before and combined the fat (vegetable oil) with the other 'wet' ingredients (eggs, milk). Is this technique used with other kinds of breads/baked goods?   Preheat oven to 375 degrees. Put fat in a 10-inch cast-iron skillet or in an 8-inch square baking pan. Place pan in oven.  Meanwhile, combine dry ingredients in a bowl. Mix eggs into milk, then stir this mixture into dry ingredients, combining with a few swift strokes. If mixture seems dry, add another tablespoon or two of milk.  When fat and oven are hot, remove skillet or pan from oven, pour batter into it and smooth out top. Return pan to oven. Bake about 30 minutes, until top is lightly browned and sides have pulled away from pan; a toothpick inserted into center will come out clean. Serve hot or warm.   
This technique is simply frying. It is used with a ton of baked goods such as crepes, pancakes and such, and also sometimes in the oven with e.g. yorkshire puddings or popovers. The comparison to muffins is not especially helpful here. You are comparing the fat which goes into the batter (for the muffins) with the fat which is used for frying (for the cornbread). In fact, these are separate and have separate roles. They can also be used independently from each other - you could bake a recipe which has fat in the batter and is then, separately, fried in hot fat in the oven. 