Already knowing the Fibonacci sequence isn't relevant:
> He was unable to explain to me how he would have implemented the Fibonacci sequence without chatGPT.
An appropriate answer could have been "First, I look up what the Fibonacci sequence is on Wikipedia..." The interviewee failed to come up with anything other than the chatbot, e.g. failed to even ask the interviewer for the definition of the sequence, or come up with an explaination for how they could look it up themselves.
> He was unable to explain to me how he would have implemented the Fibonacci sequence without chatGPT.
An appropriate answer could have been "First, I look up what the Fibonacci sequence is on Wikipedia..." The interviewee failed to come up with anything other than the chatbot, e.g. failed to even ask the interviewer for the definition of the sequence, or come up with an explaination for how they could look it up themselves.