Interesting that the "down tube bottle only" has more drag than the "seat tube bottle only". I guess that comes to the diameter of the bottle vs the angle of the bottle on the bottom tube. I would have thought the bottom tube would have more drag because it's at an angle to the direct of travel, much like the wings on an aeroplane, so the drag would tend to try and lift the rider, as opposed to rear spoliers like in cars that "push" the car down onto the road more and hence reduce friction and loss of power through being too light!
I wonder if the same amount of fluid could be dispensed from a narrower bottle and reduce the drag even further! But I am not sure it makes any difference to sprint riders though.