Rhetorical: It is most probable that the order of the Nehors understood that the Messiah would be involved in a loosing of the bands of death. They may have conflated the resurrection with the idea of salvation. Since all were loosed from death, they presumed that all were therefore saved. Amulek will tell them that salvation from death is not salvation from sin.
Doctrinal: Amulek makes clear the various aspects of the mission of the Atoning Messiah. One of the aspects is to atone for temporal death. Amulek defines temporal death as the death of the body. The Atonement will rectify this problem, and death will be defeated.
When Paul explained this same concept to the Corinthians he underlined the reversed parallel between Adam and the Christ:
1 Cor. 15:20 But now is Christ risen from the dead, and become the firstfruits of them that slept.
21 For since by man came death, by man came also the resurrection of the dead.
22 For as in Adam all die, even so in Christ shall all be made alive.
In 1 Corinthians, Paul introduces Christ as begin risen from the dead. The "firstfuits" is Paul's recognition that Jesus is the first to ever rise form the dead. What Paul does is contrast this with the situation with Adam. Where Adam was the first to die, Christ is the first to rise. Paul goes further than this, however. He indicates that all men followed the example of Adam, the first to die. He concludes that therefore all men will follow the example of Christ, and shall rise, or "be made alive."
This exact reversal of elements is intentional. Paul is emphasizing both the resurrection and the universality of the resurrection. This breaking of the bands of death is given to all men. There are no conditions attached, just as there were no options our of death from Adam to Jesus.
Amulek calls the death of the body the temporal (related to time) death. He also recognizes that there is a complete and unconditional Atonement for this death. However, he also recognizes that there is another problem. In addition to the bands of death, there is the problem of sin. What Amulek declares in verse 41 is that those sins may remain even though the body may live again. The resurrection of the body does not in and of itself have any effect on the sins of the soul accumulated while in that body.