5D Mark III High ISO Noise Reduction

I'm trying to figure out exactly how the High ISO Noise Reduction in-camera setting affects the default chrominance and luminance settings in Raw files in Digital Photo Professional. The level of NR seems to increase in proportion to ISO, which seems reasonable. The relative amount of NR is also affected by the camera setting (off, low, standard, high), which also makes sense.

Here is what I dont understand.

When I set the in-camera setting to "off", the chrominance and luminance NR settings in  DPP are usually not 0. In fact, I've seen them as high as 7-10 (at high ISOs), even with the in-camera setting set to off.

This seems to affect JPEGs as well, which suggests there is always some level of NR applied to all JPEG files, even when the in-camera High ISO NR is set to off.

Do all Canon cameras behave like this? I never noticed it on the 5D Mark II. Why doesn't off mean off?

thanks