I'm trying to wrap my head around the Environment Preview and from my point of view, it's not as impressive as it should be except for the Diffuse IBL light.  The Prop does not contribute anything towards the illumination of the scene and most of the Material Room features are inactive except for emission, but as I determined do not contribute anything to the scene.  The only 2 factors that illuminate the scene are the HDR Background, which always worked in P12, and the Preview Light.  So, if you want more defined shadows, either turn down the intensity of the Preview Light or turn it off and add your own light array.