To my understanding, if we zoomed in close enough and viewed the shoe from a grazing angle, the actual surface of the shoe would still actually be smooth physically, because we are only making this illusion of roughness with the light, right? The underlying mesh is unchanged, and we are simply altering the normal map to change the BRDF? Is my understanding correct or perhaps flawed?

From my understanding, you have various ways to approach this. You can either have an object with vertices to simulate the texture or apply a normal map to simulate this. The benefit of using a normal map, however, is in boosting performance as it is less costly than modeling the texture.

Couldn't this more complex material be simulated through use of normal maps?