I just vent back to this, I misread a part - you're right, while holding down left mouse button and panning around in the "color-map" in the bottom, you can se the nearest cmyk value for that color. That's all good, but when you release the mouse button, the values (also cmyk values) are alll different.
As a programmer I think it does a recalculate when you release the button, that should not happen.
That's a truly annoying bug - there's a workaround but remembering the cmyk values, but c'mon man
But again, I usally (when working in cmyk) use the sliders, takes some time to get used to.