You had brought out a similar point regarding Abraham's sacrifice as a test of faith and devotion to God as opposed to a ransom or atonement for some sin he had committed. I suppose that a Christian reading the Quran would tend to interpret it according to his own beliefs rather that what is drawn logically from the text. We have no concept of a blood sacrifice for atonement; however, we often will offer extra prayers, fasting, charity or other good deeds to offset some sin or bad deed that we have done. Please, correct me if I am wrong.
It is the sacrificed life and blood of the animal that makes atonement for sins according to the Bible. This is also the reason given as to why blood is prohibited for food.
Leviticus 17:11-12 "For the life of a creature is in the blood, and I have given it to you to make atonement for yourselves on the altar; it is the blood that makes atonement for one’s life. Therefore I say to the Israelites, “None of you may eat blood"."
Hebrews 9:22 " In fact, the law requires that nearly everything be cleansed with blood, and without the shedding of blood there is no forgiveness."