In Christian mortalism, what sets apart people who have lived from people who didn't live?

According to Wikipedia , "christian mortalism" describes the idea that the soul is not immortal, but dies together with the body and rises in the resurrection. Proponents of this are Jehovahs Witnesses, some Lutherans, Seventh-Day adventists and some others. Since the soul is dead or dissolved after death, that means God recreates it for the resurrection, as a body that is dissolved would need to be recreated. Since God is omniscient, not only does he know how each person would behave before they are born, this arguably also means that he knows how any potential person would have behaved if given the chance. Then, what is the difference between someone actually having gone through life, now no longer existing after death except for in the mind of God, to a person never having existed except for in the mind of God? In a sense this is asking what value the life-on-earth has, but I want to expand it in this sense to add the notion of how could God not grant resurrection to a person never having existed when that person is not fundamentally different from a person who has lived (both just existing in the mind of God after the latter person has died).