it depends. ask it a hard question and then ask it an equally hard question that incorporates the answer from the first to make it easier, such as computing the n-1 digit after asking it to compute the nth digit. A human will take a long time to answer the nth digit question but then by using the first answer will solve the second one instantly. The AI with delay will take equally long.
Just make the second delay shorter. An attacker can quickly implement this while the defender had to spend time thinking of the idea, implementing the new question, and adding the infra for catching bots who answer the 2 differently than humans.
Delays are not good proofs of humanity because computers can wait too.
