We are largely talking about adjusting different things here. Adjustments made to the RGB/HSV values in a graphics editor only affect the selected colour. Adjustments to the image colour balance and contrast in graphic editors usually affect all colours equally. The image shown in a graphics editor is also usually static.
In TANE and TRS19 the scene is dynamic in time, the lighting characteristics change during a 24hr cycle. This has different effects on shadows, indirect lighting and direct (sunlight) lighting as well as brightness and the effects of fog, all of which will change according to the time of day. These effects also vary with the season.
While the colours (RGB/HSV) of the individual assets are fixed by the creator (ignoring seasonal effects such as snow), those colours can change under different lighting conditions such as shadow, direct and indirect lighting. Objects in shadow will be affected differently from those in direct sunlight, for example.
All of this is much more complex, hence the need for time control points placed around the clock.
Personally, I think that N3V has come up with a very good set of environment tools with some tweaking still needed - such as the ability to enter numerical colour values.
