1. Missing face embed plates
2. The black 'track' is within the building plane.
3. New energy codes really preclude curtain wall of any significant amount for residential
4. Cost delta
Now that you have weighed in 'O, I am this close to certain that it is a curtain wall. If you look at the right of the photo you will see that the curtain wall passes in front of the slab end. When I first glanced at the photo I was looking at the uppermost part of the curtainwall and ignoring the rest, noting that it was hard to tell (curtainwall or window-wall) without a closer look. The upper portion of the wall is held in place with an under-slab angle (although we can't see it in this photo -- to your point number 1). The "black track" then is not within the building plane -- to your point number 2. The energy codes actually prefer curtainwall to your point #3. And the "cost delta" has no place in this discussion.
Another advantage of the curtainwall approach is that vertical banding from ground to roof is made possible with different color tones. I am not saying that that is what the Hat people are planning, but their renderings suggest that it is not outside the realm of possibility. It will be interesting to see the progress.