And it's a very good question, which the Cornell box test is meant to ask. There is supposed to be an exact real world counterpart which you can compare this image with, and from there you would be able to highlight the exact differences. (But this was hacked together with default HL2 textures, so no real Cornell box exists for it.)

I suspect the excessive brightness of the white surfaces in this scene is a result of the bloom shader only calculating a surface's color and illumination (e.g. no reflectivity or roughness), hence fully-lit white surfaces are blindingly bright. There's a new generation of games that will be using 'physically-based' rendering that will hopefully be prone to fewer of these flaws, as they don't use color to determine brightness.

Also, see the strange shapes on the back wall. Those were what surprised me most when I first compiled this map.

What is it about reflections in video games that they just cannot get right? I mean, this looks as good as most anything a person finds and even here you can see that they walls look unnaturally flat and the white portions are awash with reflection to the point that they appear to be as luminous as the source? This is not a criticism of this work, just merely a question...