I think that hump on the rear bracket is to clear the AC evaporator drain plug. Think of it this way, if the bracket is indeed used to cover the drain hole, then there won't be a screw hole in the center. So the bracket with two holes goes over the drain plug, and that bracket mounts where the hump goes over it. Then bracket with one hole sits flush against the tunnel, with the hump facing down. The photo by keshav is a repop from cswerke. He may have mounted the brackets wrong when staging the photo.
With all of that said, as you can see from the square steel washer, mine has been tinkered with in the past. Likely due to the awesome 10 speaker 80’s stereo that I removed. Mine could be wrong also, but it is mounted and secure in the vehicle. To mount it incorrectly would mean that the installer would need to drill new holes in the tunnel.
You need one more set of photos.