Simply put, it emphasizes the manner in which God saves redemptively through the historical reality of the Savior (that is was a true event in time and applicable to everything in the bible).
The focus is grounding everythinig in the reality of the historical context of a real Jesus, real virgin birth, real life, death and resurrection. That Christ, then, speaks to everything that is exegetically tenable about what is happening through every page of Scripture. Everything is grounded and seen in the need for redemtoion because of sin, and by the cross.