You could argue that behind the brain of a chess master is also a “series of rules and heuristics”, but as this series may be infinitely long and isn’t feasibly

You could argue that behind the brain of a chess master is also a “series of rules and heuristics”, but as this series may be infinitely long and isn’t feasibly determinable it’s difficult to say in what sense that’s actually true. Further, it’s likdly that the series of mostly-linear transforms in AlphaZero (or, the series of neurochemical transforms in a chessmaster’s brain) is the only form in which these rules would be efficiently computable. One way of looking at the difference between AlphaZero and traditional game AI is that the former uses irreducibly conplex heuristics (as far as we know,) just as we think brains are capable of.