In response, Nicodemus said, “How can a man be born when he is old? Can he enter a second time into his mother’s womb and be born?” (John 3:4). Did Nicodemus really not understand what Jesus meant?

Don’t imagine that Nicodemus was so naive as to think Jesus was telling him he literally needed to be physically reborn. Nicodemus must have been a highly skilled teacher himself, or he would not have attained his position. His question to Jesus should no more be interpreted as a literal reference to physical birth than Jesus’ original remark to him. His rejoinder to Jesus merely picked up on Jesus’ imagery.