The Diffuse Render Element is useful for changing the appearance of many passes, when it is combined with Raw render passes (like Raw GI, Raw Light, etc.).
In the example, the Diffuse Filter is blended with the Raw GI RE in Multiply mode to provide the Global Illumination element. This way, color correction can be performed upon the raw pass, without the actual diffuse colors changing, making it possible to tint a pass in a realistic way without re-rendering.
