And that must be why an 8KHz downsampling of a CD has more than double the dynamic range of the original, right? You can google theorems, fine, but apparently have no idea what they mean and where they are applicable. So you must work at DXO, then?
The downsampling will reduce the bandwidth but increase the resolution of the samples. You trade off precision in the amplitude (quantisation noise) for bandwidth (loosing high frequencies). This is exactly the same as happens when you down sample a digital image - and just as you might not want to listen to all your CDs at 8KHz you probably don't want to print out all your images at 600x400 no matter how much this improves the DR.
I posted the Google links as they are usefully informative on the subject. You, rather than posting an informed and referenced response, just posted an insult (FYI, I am a Physicist who has worked with DSP and signal processing for more than 20 years, and I have no connection to DXO).
Try a test--take a D800 photo of Stouffer wedges, push exposure in post how much you like, and make a note of the darkest one. Now downsample to 1/64, i.e. ~0.5mpix and repeat. How many extra wedges appeared? Exactly as many as how much the *oversampling theorem* is applicable here--i.e. zero.
Well, I do not have a D800 to test (and have not commented on this specifically).
I find that the DXO measurement data matches pretty well my experience when shooting with those cameras that I have (GF1, 40D, 5DII, 5DII). You can take issue with the fairly arbitrary criteria that they use to produce their overall scores and I am sure that DXO sometimes make mistakes, but the individual measurements - if you understand what they are - have always looked pretty good to me and correlate well with my experience of the 5DIII (particularly when compared to the 5DII).
Simply wanting something to be different does not make it so.