Is that last bit from the Copyright Office, or is it the author's interpretation? Because I could just as easily imagine the battle being over who or what was the actual creator of the content (i.e. is it a derivative work), rather than whether the thing the machine created is eligible for copyright.
To remove the AI from the equation for a second, imagine that I took four images of living artists' work, placed them in a 2x2 grid, and called that a new artwork. There are two seperate questions to consider: (1) have I infringed upon the original authors' copyrights, and (2) is the new thing I have created eligible for copyright.
The stance that there is "no copyright protection for works created by non-humans" only addresses the second question, not the first question of how it interacts with existing copyrights.