First, a good player can't be accurately predicted at all; the conclusion from game theory is direct and clear. This is a case where a strategy involving picking moves at random is superior to any deterministic strategy.

Second, your rebuttal is not especially good support for the idea that we should be trying to solve the problem with a technology specifically designed to imitate humans.

How good are human players, by that metric?

That's a fair question. I know of related research showing that chimpanzees are much better at achieving the correct distribution of strategies in asymmetrical-payoff games than humans are. The obvious implication is that a typical human isn't that good at being unpredictable.

The distribution of people who enjoy playing fighting games will probably look somewhat different, though.