Yes, everything you've said is true. But the organization chooses the title, and Keller is a VP of that organization. Neither Keller nor Duncan are to be confused with Ken Ham. They are thoughtful, well-spoken men. Nevertheless, both are doing what Ham does, which is to make the special creation of Adam essential to the gospel, or as Keller calls it, "the Pauline understanding of salvation."
The question that both responded to comes around 4:30. Here is my rough transcript:
Russell Moore: When you’re working together … We’re in a church, or we’re in a ministry … What are the essentials, in terms of, these are the boundaries we all have to agree on when we’re talking about creation in order to recognize one another as orthodox, and as teachers within the church?
Keller's response comes around 8:00, and by referencing "With the Christian," he shows that he still has the original question in mind and agrees with Duncan, who earlier emphasized the de novo creation of Adam as an essential....
With the Christian I do go to Adam and Eve, too. There are a lot of understandings of how old the earth is, and there’s a lot of different understandings of what the days are in Genesis 1, and to what degree evolution was part of how God created things … And I would say there are several gradations. There are four or five or six approaches … There are. But I say where I would stop is with Adam and Eve. And I would say not only was there an actual Adam and Eve, but otherwise I do not understand how the Pauline understanding of salvation works….
It seems a fairly inescapable conclusion that the video portrays belief in a literal Adam & Eve as a boundary marker for orthodoxy. Like @DeborahHaarsma, I would hope that The Gospel Coalition is not making that their official position.
Edit: Added the portion "and agrees with Duncan ... as an essential."