It would appear Epic was already in the process of changing the color grading controls to what you suggested in the video 
From the 4.15 release notes:
NEW: COLOR GRADING CONTROLS
We added all new controls for the Color Grading properties in Post Process settings that provide a more intuitive experience and more precise control.
Highlights of the new controls include:
Colored lines under each slider denote which color channel the slider is affecting.
Sliders have improved precision when you edit the value. You can also press the Shift key while editing to increase precision even further.
A new color wheel modifies the X, Y, Z channels all at once. A slider under the color wheel controls the amplitude of the X, Y, Z channels