I do not understand what anyone stands to gain from this. As I understand it, you are comparing images taken the same exposure level (same f-stop and shutter speed) but with different ISO speed settings, and thus with different amounts of exposure compensation in post-processing. Specifically, ISO 100 with about four stops of underexposure and thus massive "brightening" needed in PP compared to ISO 1600 setting with exposure giving roughly the desired output levels with little or no PP adjustment needed.
What is the point? Surely in general one would use the latter, higher ISO speed option, and never have reason to about whether or not it is slightly better than the never used option of "ISO 100 and +4".
The comparison using 'same exposures' is to demonstrate graphically and clearly that there is a real
and unequivocal advantage to using a high ISO (with Canon cameras) that is not just a software fudge. This has not always been the case. The following image taken with my D60 at ISO 400 demonstrates this point very well.
It was necessary to use ISO 400 for this shot in order to get the White Herons sharp (1/500th at f5.6). The exposure was pretty close to a full ETTR, requiring a minus 0.5EC adjustment in ACR. But have a look at the shadows.
There's room for improvement here and the improvement has been delivered by Canon, in spades.
Image Stabilisation and high image quality with a small amount of light are high priorities for me when choosing a camera, and Canon has it. I think it's fantastic I can use my 5D, handheld, for street photography at night without a flash.