the map has been designed with a band of adjustability within it with the fuel maps, boost maps and the timing. Essentially you can adjust your settings to the weather conditions, or new mods safely (as long as you log the car to check) to ensure the car is always at the optimum.
i guess its sort of similar. however adjusting the boost will have an effect on both timing as fueling so in a way it is better than a boost controller as you can fine tune it to a certain degree.