"Is Cycles" geometry node. For realtime preview of millions of instances without sluggish opengl viewport

In blender since we don't use a dedicated IPR large scale scattering can become difficult. This would only be useful for cycles rendering. Evvee would always suffer from the draw time of instances.

In cycles however, the viewport stays very fast even with millions or billions of instanced polygons.

If we had an "Is cycles" geometry node we could switch to a proxy (single or scattered points) / hide the objects

here's a mockup

and a video demonstrating the difference