Yes and no.

Chess bots (like Stockfish) are trained on game samples, with the goal of predicting what search path to keep looking at and which moves will result in a win. You get game samples by playing the game, so it made sense to have stockfish play itself, since the input was always still generated by the rules of chess.

If a classifier or predictive model creates it's own data without tying it to the rules and methods in reality, they're going to become increasingly divorced from reality. If I had to guess, that's what the guy in the article is referencing when talking about "sanitizing" the data. Some problems, like chess, are really easy. Mimicking human speech? Probably not