> If it's just the built-in AIs, you're right that it's much less impressive. They should be winning 100% of the time.

Absolutely. Unless the win-loss ratio includes all games while the AI "learns" to play the game. It might have lost most of its early games, but now wins 100% of the time.

I suspect it wouldn't take DeepMind long to master starcraft II and beat starcraft's AI 100% of the time.