An interesting comment:

The European champion of Go is not the world champion, or even close. The BBC, for example, reported that “Google achieves AI ‘breakthrough’ by beating Go champion,” and hundreds of other news outlets picked up essentially the same headline. But Go is scarcely a sport in Europe; and the champion in question is ranked only #633 in the world. A robot that beat the 633rd-ranked tennis pro would be impressive, but it still wouldn’t be fair to say that it had “mastered” the game. DeepMind made major progress, but the Go journey is still not over; a fascinating thread at YCombinator suggests that the program — a work in progress — would currently be ranked #279.