Directional lights and skylights works out of the box as real world lighting models and how things like shadows behave requires value adjustments in areas that seem at first glance has no relationship to the desire to control shadow density. In this example you can force the desired result by increasing the indirect lighting intensity to bled off the shadows.
Another option if you are looking to create a solid lighting base is via the use of HDR cube maps added to a post process volume.
Point lights can also be used as kickers for force the result.
