The central tenet behind The Gospel You've Never Heard is that the Jews who wrote the New Testament did not think of the term "salvation" in the way we have been led to believe. The Jewish understanding of salvation (as made clear in the Later Prophets, among other places) is that of God vindicating God's people. It is then, of course, about what it means to be "God's people," which leads us into the discussion of the Holy Spirit and the cleansing of the New Covenant temple.
Anyways, Mark 13:20 is a stark exposition of this primary Jewish understanding of salvation, blatantly showing that the modern understanding of "deliverance from Hell" is totally out to lunch.
Mark 13:19-20 discusses God's Judgment that is coming against the world. Jesus says "In those days there will be suffering unlike anything that has happened from the beginning of God's creation until now, or ever will happen. And if the Lord had not cut short those days, no on ewould be saved. But because of the elect, whom he chose, he has cut them short."
This is the setting for the oft-quoted "He who calls upon the name of the Lord shall be saved." [Acts 2:21, Romans 10:11, both quoting Joel 2:32 (or 3:5 depending on which Bible you have).]
Now, if "saved" here refers to "deliverance from Hell after death," then the importance of this wrath being short-lived "for the sake of the elect" is absurd. To say that "no one would be saved" if this wrath were prolonged upon the earth makes no sense with the modern understanding of salvation, for the modern understanding of salvation only has jurisdiction after the grand resurrection. Christ's focus is not on the Judgment that comes after the resurrection but on the wrath that comes before it. This is the focus of apostolic Christianity and dominated early church thought for the initial generations of the church. This is why Paul calls Christ "our savior from the coming wrath." This is why Peter has to inform his readers not to be perturbed that the day of God's vindicating them has been postponed. The early church, must as the Jews who came before them, were focused on God's vindicating them over their oppressors. Luther wasn't around to tell them that they all begin "by default" in hell and needed deliverance from it. Such a notion would have seemed ludicrous to Paul.
This notion of salvation as "deliverance from the coming global, physical wrath" is linked to the other primary notion of salvation as "deliverance from domination by our flesh" because they both are connected to the idea of being in covenant with God, for the Holy Spirit is the seal of the New Covenant and is sent to help this covenant succeed where the earlier one failed. This second definition of salvation, the one Christ describes when saying "Those who sin are a slave to sin, but if the Son makes you free, you are free indeed" is connected to a rather secondary definition of "saved" as the physical transformation achieved after the resurrection. The receipt of the Holy Spirit is a type of salvation in that we are no longer enslaved to sin. The receipt of a new body is the completion of this.