When using deferred shading and no "global/default" reflection probe, the deferred reflections fullscreen pass for it is still done. This costs a small amount of time on the GPU, for no good reason.

-Play the game.
-Check using the framedebugger, pix or renderdoc.
-Notice the RenderDeferred.DefaultReflection pass using a blank black cubemap.

It is expected that if no default cubemap is used, this pass is not made.