Why should we not expect the Redeemer in the opening of Matthew?
The opening of Matthew presents Jesus in His royal lineage as the King of Israel, the son of David, fulfilling God's promise of a royal house. Only later is it revealed that He will also be the Redeemer. So readers should not run ahead of what has been revealed up to that point.
Les explains that after the genealogy, Matthew moves to the birth account in verse 18. Mary was espoused to Joseph, and before they came together she was found with child of the Holy Spirit. Joseph, being a just man, planned to put her away privately, but the angel of the Lord appeared to him in a dream and called him “Joseph, thou son of David.” Les asks why this is instituted here: to show that Jesus is in that royal family. He connects this back to 2 Samuel chapter 7, where God promised David that beginning with him would be a royal house and a royal family, and down through the ages that royal family would be the ancestors of the King. That is who Jesus is presented as in the opening of the New Testament. Les cautions not to run ahead of what has been revealed so far: all we are to understand at first is that the King has made His appearance. Later it will be revealed that He is also the Redeemer, and still later there are further revelations. For now, the emphasis is that He comes to be the King of Israel.