He said "bluff" body, not "buff" body
It's interesting that the larger square body is blocked by the smaller round body, while the larger round body is blocked by the smaller square body.
Experiments with this might be easier than boattails and such. You can place something on a pole out in front of your vehicle and keep an eye on it, while you can put tufts on your windshield where you can see the effect without cameras.