When the interviewer asks you to write a loop but you've been optimizing code since the Pentium era. Why waste precious CPU cycles on branch prediction and loop overhead when you can just manually unroll that bad boy?
Sure, it looks like you're writing code with your face, but technically you're just doing the compiler's job for it. Modern problems require ancient solutions that haven't been relevant since 1997.
Your interviewer is either going to hire you immediately or quietly escort you from the building. No middle ground.