Thanks for reminding me about this. This led me to consult my copy of The Reason for God, where Keller writes about his view on Genesis 1 and 2. Seems like he does endorse a difference in hermeneutic between them. However, he does not elaborate in detail the specific textual reasons why (and neither in the famous TGC video). Maybe there are good arguments for this distinction.
The difficulty comes in the few places in the Bible where the genre is not easily identifiable, and we aren’t completely sure how the author expects to be read. Genesis 1 is a passage whose interpretation is up for debate among Christians, even those with a “high” view of inspired Scripture. I personally take the view that Genesis 1 and 2 relate to each other the way Judges 4 and 5 and Exodus 14 and 15 do. In each couplet one chapter describes a historical event and the other is a song or poem about the theological meaning of the event. When reading Judges 4 it is obvious that it is a sober recounting of what happened in the battle, but when we read Judges 5, Deborah’s Song about the battle, the language is poetic and metaphorical. … I think Genesis 1 has the earmarks of poetry and is therefore a “song” about the wonder and meaning of God’s creation. Genesis 2 is an account of how it happened including Genesis 1. But it is false logic to argue that if one part of Scripture can’t be taken literally then none of it can be. That isn’t true of any human communication.
What can we conclude? Since Christian believers occupy different positions on both the meaning of Genesis 1 and on the nature of evolution, those who are considering Christianity as a whole should not allow themselves to be distracted by this intramural debate. The skeptical inquirer does not need to accept any one these positions in order to embrace the Christian faith. Rather, he or she should concentrate on and weigh the central claims of Christianity. Only after drawing conclusions about the person of Christ, the resurrection, and the central tenets of the Christian message should one think through the various options with regard to creation and evolution.
Keller, The Reason for God, Chapter 6, p. 97