AMR, you are misreading what Bob Hill wrote:
You latch onto the sentence, "God the Son could not die," as a proof text that Bob Hill agrees with you and disagrees with us. But in the context of the rest of the paragraph, Hill is clearly saying that God the Son could not die prior to His incarnation. Bob is saying that God the Son became a Man (Jesus Christ) so that He (God the Son, now a.k.a. Jesus Christ) could die for our sins.Bob Hill said:Jesus Christ could die for our sins only as a perfect man. God the Son could not die. That’s why He had to become a man and live for 30 years without sinning.