You're right, but I do wonder if they're misremembering their prompt a bit. The AI's response would be much more likely to arise if the prompt was something closer to "find both issues that are critical and related to X". Based on my own experience, it would be a very surprising mistake for the AI to have made if the prompt really was as straightforward and precise as "find issues that are both critical and related to X". I know it's a bit annoying to question someone's account of their own experience, and obviously I'm not saying this couldn't have happened, but my guess would be that the actual prompt was at least somewhat ambiguous.