Maybe I don't catch the point, but was this vision supposed to characterize the sacrifice of Christ for our sins? The one from whom no one took his life, but he laid it down of his own accord? We didn't choose to cause Jesus Christ to bear our sin. God the Father chose him to bear our sin.
Allegory - The Holy Eucharistic bread and wine is the actual blood and body of the sinless Christ which Christians consume. The Saracen saw the vision of the bread and wine transformed to the body and blood of Christ which being sinless was processed in the Muslim's mind as being like a baby. In other words even though the man was a Muslim it seems he was a righteous man and saw the Holy Eucharistic miracle before his eyes but not being a Christian could not process and comprehend what he saw.