I wonder if you have Canon's documentation on this?
Canon doesn't publish such documentation. But consider - we have an observation by the video crowd that multiples of ISO 160 are cleanest, and that's backed up by Bill Claff's measurements. There are two hypothesis to explain that observation, one that multiples of 160 are cleanest because they're multiples of base ISO (which was suggested to be ISO 160, but could easily be ISO 80), the other that the are cleanest because they're pulled from the next-highest real multiple of base ISO, i.e. 100, 200, etc. DxOMark's measurement data are reliable, and they measure the base ISO of the cameras in question as ISO 80, not ISO 100. That supports the first hypothesis, and means ISO 100 is, in fact, pushed from ISO 80.
Also, what do you think about the Dynamic range of iso 160 vs 100?
Based on Claff's data, DR is highest at the same multiples of ISO 160 that are least noisy - a win/win, IMO. As with noise, the 1D X has a smooth curve for DR vs. ISO, not jagged like other Canon cameras.
As Mt. Spokane stated, this concept is useful for a planned shot with setup time, less so for fast moving situations. In the latter case, Auto ISO is often a useful option, and even if you restrict the ISO setting to full stops (which I do, simply because it makes setting the ISO faster), Auto ISO will use the 1/3-stop increments. Personally, I'd take a little more noise in a shot with ISO 500 to missing the shot because I was trying to set ISO 640 instead. Fortunately, with the 1D X I don't have to worry about it, since the curve is smooth (and at all ISO values except 160, the 1D X has lower read noise than the 5DIII).