From a quick read of the first part of the book, I understand it like its a radio stations for the main class. So the radio stations sends out all of it signals for whoever wants to tune in and listen. For example like in the book, the achievement script tunes in to the specific condition for the achievement. Like you would tune your radio to listen to a desired station.
I feel this will make the code much simpler, I still not sure of how the coding will look until I have tried it out for myself. I am a do and learn kind of guy.