With the sun and the clouds in the HDRI the artist is limited to position the HDRI so that the sun shines from the desired location and live with what clouds are visible, or the other way around. By taking out the sun from the HDRI the artist gets full control over the clouds in the sky without losing the ambient light. Bryce has the means to blend HDRI light and the light of its own sun with the HDRI backdrop, haze, sky color, more clouds, etc. With a real but sunless HDRI sky the artist has all the freedom to make any sky fitting the landscape and mood.