I cannot be certain about the specifics of this type of rendering by NVIDIA. However, tile-based rendering can lead to other optimizations such as hidden surface removal, the broad term to define this.
What happens is if a scene is properly rendered with opaque geometry first, then alpha-blended geometry sorted back-to-front, entire objects can be discarded completely. Fragment processing would not proceed after this as well, as per usual rasterization.
So if a tile is detected as completely opaque, then triangle that lies completely behind the Z/depth values in the tile would be discarded and never even processed further.