"Here are the basics: There is no dynamic difficulty on Hard. Only on Normal. The difficulty factor changes when you lose or win. It is clamped between 0.5 and 1.5. The factor starts at 1.0. On a loss, it goes down by 0.15. On a win, it goes up by 0.075. The AI target dish score range target is multiplied by the difficulty factor to get a final range for the AI to shoot for. It is possible, especially in weird duels with poison or easy duels due to story reasons, for the AI to fail to adhere strictly to the designed range. That is, the AI can score higher in a rematch just due to the randomness of the AI system.

Hope that helps and happy speedrunning!"

quote from the developer