Just to clarify, I am only referring to noise and smudging from TS posting.
IMO these are considered noise reduction tools. While better software tools can recover grainy images and in some condition improves picture with dark area noise but they cannot fix severe color noise and smudging.
I cannot remember which brand of camera (maybe panny) but the camera actually takes 1 extra image at lower iso to top up the area where the processor cannot determine the final color. I think is concept is the same as zero-noise software.
If comparing same lighting condition, high iso colour will fade. And depending on sensor, some does badly (e.g Sigma).