Thats because render point 0 and 1 (where motion blur and the red test shader were set to render at) is before the alpha blended meshes are rendered, so lens flares, explosions, glass etc is rendered on top of the black screen.
Thats essentially what the old fake hdr (now removed) subsystem did. Scaling down the scene to 1x1 to get the average luminosity then increasing or decreasing the brightness over time to the prefered level. The brightness is picked up by the bloom shader and bloom is applied accordingly. Depth is available to shaders so i don't see why you couldn't have more bloom on a close up, but you'll have to try it for yourself, thats why its open source. If you get error messages when you pp_load theres a broken shader.
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