SkyLight Movable or Stationary?

Following this UE4 Neutral Lighting Scene Setup and confused when the author says your SkyLight should be set to Movable.
Shouldn’t it always be Stationary like your Distant Light(Sun)? I’m confused.
​​​​​​​https://youtu.be/jyq11xOp-B4?t=632

Directional Lights/Skylights are usually stationary unless you plan to move the sun (such as a game with a day/night cycle).

In this particular video, however, he seems to just be trying to make sure that lighting doesn’t affect the colors or “neutrality” of the scene. I’m not sure if there is something inherently more neutral about movable lights or if he just doesn’t feel like having to build the scene over and over again when he is teaching.