So, he managed to find perfect answers to the most difficult parts of the exercise in 30 seconds, and then struggled for 30 minutes, with my help, on getting the print right.
Of course, I used a slightly modified version of well known problems like "Fizzbuzz" and other stuff, mostly as a quick start to get into the real engineering challenge. It explains why ChatGPT was absolutely unable to finish the exercise. During the interview, it acts a a good filter. If it last 3 minutes, fine, no signal ; but if someone is struggling on it for half the interview time, it's a clear "No".
I haven't check if the candidate was invited to later rounds, but considering my negative review I think he was rejected.
I'm afraid these tools are not going to help you when things really matter :)