It looks like a half-baked design element. From what I can see in the pictures, that part of the curtain wall has a unique mullion pattern, so the architects chose to distinguish it further by extending the curtain wall past either edge of the building.
Doesn’t really work here imo, because it’s too subtle and seems like an afterthought. This works well if integrated into the overall concept of the building. Example: 200 4th street in Nashville, where the glass is meant to be an expression of four pages of sheet music.