"depthTextureMode = DepthTextureMode.None" does not work?

Hello,

I created a new scene and created a cube.

Play and open Frame Debugger window.

It showed Camera.Render / UpdateDepthTexture / Draw Mesh Cube is executed.

So, I attached this script to camera.

 void Start () 
 {
   GetComponent<Camera>().depthTextureMode = DepthTextureMode.None;
 }

I expected UpdateDepthTexture is not executed, but result is not changed.

I tried all modes, got below results.

DepthTextureMode.None -> execute UpdateDepthTexture

DepthTextureMode.Depth -> execute UpdateDepthTexture

DepthTextureMode.DepthNormals -> execute UpdateDepthTexture and UpdateDepthNormalsTexture

It looks like DepthTextureMode.None does not work ... why?