Are the color grading tools just another way of adjusting color instead of using the Curves or Hue sliders? Does it offer additional functionality that can not be done with the other tools or is it really just trying to mirror the types of tools available in video programs?
The Color Grading panel is different than other color features in several ways.
Most other panels apply the same color adjustment to all levels from dark to light. So if you want to color-shift highlights, midtones, and shadows differently (without using masks), that is not something you can do except with Color Grading and RGB Curves. But separate RGB curves are difficult to control and keep balanced. Color Grading makes it easy, and with its Blending and Balance options it can be faster than trying to do the same thing with range masks.
Hue is available only as a masked adjustment, and it completely replaces a hue (not much trace of the original color). Color Grading is different because it isn’t intended to replace a hue, only to shift it.
Those are some technical reasons. But there are also workflow reasons why Color Grading is not the same. Especially the way video editors see it, color correction and color grading are always separate and different steps. Color correction (technical color balancing) is always done before color grading (creative expression). Most Lightroom panels are about color correction, but Color Grading is intended as that post-correction step of creative color expression. Correction almost always needs to be done; grading is often optional.
It’s a good question, because some mistakenly think the Lightroom color panels are just different controls of the same math. But that isn’t true, every color panel in Lightroom is unique. Each panel technically changes color differently, no panel is redundant with any other.