In this video about making chocolate chip cookies, eggs are the last ingredient added.
This is different from what I've learned so far; what's good about this method?
In home recipes the eggs are added whole. They can't be added until after the creaming step or else they will dissolve some of the sugar. They are added before the flour to make sure that the yolks and whites are completely blended.
In this video- the process has been simplified for industrial quantities.
In the step that can't be skipped, the fat and sugar are creamed. All the other ingredients are then added at once and mixed. You can see that the eggs have already been blended with the vanilla so no extra mixing is needed for them.
I have never seen a recipe where you add a liquid after you have added the dry, at least anything other than water.
Before dropping in dried goods, you want to sift or whisk them together. This ensures proper dispersion of the crucial ingredients (baking soda, spices, salt, etc.) This is also true of the wet ingredients.
The butter is generally creamed to aerate it. The sugar 'punches holes' in the butter, allowing bubbles for the leavener to expand. Mixing the egg at this point means all the liquid fats and binders will be properly mixed through-out the dough. Adding the eggs afterwards may leave clumps of fat or protien in the mixture, which could affect the final product.
In general (and certainly for cookies), you mix sugar and butter (creaming), then one egg at a time until mixed, any other liquids (vanilla, molasses), and then start adding the mixed dry ingredients.