scarlock, I think you are just misinterpreting what your eye is seeing in the image.

Assuming you have no fresnel effect in the box material, the only difference in the actual strength of the floor reflections from the box sides will be due to the variation in diffuse lighting levels of the floor itself.

So the rear (reflected) surfaces of the box are not 'reflecting more of the floor' than the sides in direct view. It only appears to the eye that they are.

Why? Simply because of the very low diffuse reflection on those unlit sides of the box - pretty close to zero. That's the reason you can see the floor reflections much more clearly, not because they are any stronger.

Izi

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)