This isn’t entirely accurate, although it describes the AlphaGo we saw last year. What played Ke was different.
"... about a year ago, DeepMind redesigned the system. In essence, they built the new AlphaGo without help from human moves. They trained it entirely from games where the machine plays against itself--part of a continuing progression toward AI techniques that truly learn on their own. 'AlphaGo has become its own teacher,' says David Silver, the project’s lead researcher."