Oh you are right. Somehow I didn’t realize you can actually deactivate it 
But there is one benefit. The RT white balance works much better in correcting strong shifts in the white balance of the scene. Lets say very warm tungsten light is the light source. You can correct this after picking your white balance spot within Film negative tool.
Also i had problems before with Kodak Vision 500T film because its a Tungsten Balanced film. If you shoot in normal daylight and follow the guide then it’s very hard to use the red/green slider to get anything that looks realistic.
But using the RT white balance after selecting my film base white point you basically can change the film to be daylight white balanced (or think of it to virtually change the background light source to be more “warm” or “cold” color)
After this use the red/green slider to set the colors. I was surprised how well that actually worked.