> There's also the fact that some of the unexpected moves were apparently more about solidifying against a loss than increasing the magnitude of a win.
Humans play that way too. Everyone wants to maximize the chance of leading by >=1 stone.
The difference is that AlphaGo is better at calculating a precise value of a position, so that when uncertainly plays in, AlphaGo can play for, say, "1-3 stone lead", while a human can only get confidence in "1-7 stone lead", and thus needs to play excessively aggressively to overcome the uncertainty.
Humans play that way too. Everyone wants to maximize the chance of leading by >=1 stone. The difference is that AlphaGo is better at calculating a precise value of a position, so that when uncertainly plays in, AlphaGo can play for, say, "1-3 stone lead", while a human can only get confidence in "1-7 stone lead", and thus needs to play excessively aggressively to overcome the uncertainty.