As the manual says, the SCENE flag draws an infinite z value into the z buffer. This has nothing to do with clip_far, which is the maximum distance of an object to be rendered. The SCENE flag does not affect clip_far.

For an object to become the sky, the SKY flag must be set. In your code above you have a view entity at an infinite z distance. The difference between a sky and a view entity is that the sky entity is rendered in the background, the view entity is rendered in the foreground of a view.

I hope this helps.