Here is my guess: Usually marks are given for partially correct answers, partially to be less punishing for human error whether caused by stress or other factor

Here is my guess: Usually marks are given for partially correct answers, partially to be less punishing for human error whether caused by stress or other factors, there’s a good chance the student understood the topic. If instead they are using a chat bot, but didn’t catch the mistake themselves, it’s an indication of less understanding and marked accordingly.