Quote - Doesn't have to just be a ball bearing.

I think Fran's puzzlement is regarding the supposed benefit of the ball bearing reflecting the inside of a sphere (with a photograph of a room mapped to it), as opposed to the ball bearing reflecting a room (scene) made in Bryce.

If so, I share that puzzlement. I can see that it might save some modelling time, but I can't see that it's especially relevant to simulating HDRI lighting.