If a render target calculates depth, can you turn it off?

I recently learned from these examples that render targets calculate depth. Building Effects with Niagara and Blueprint | GDC 2019 | Unreal Engine - YouTube
https://answers.unrealengine.com/questions/764696/capture-depth-from-render-target.html?sort=oldest
I found this very surprising. For what purposes besides that cool hologram in the video, would they have put this in the engine?

More importantly, is there any way to turn depth calculation off to save on performance? I want to use render target for a minimap, and have no need to be calculating the depth of every pixel. Thanks!