How the pre render frame / draw call workds

Hello, I have a theoretical question about Pre-rendering frames/draw calls.

Let’s say we are on a situation with Low latency mode set to Ultra ( Pre-rendered frame = 0)
We are in the situation of GPU bottlenecking so the time spent by GPU to render frame takes much more time than CPU to work for the draw calls.
I know when CPU starts to work on the first draw call and finishes the work and sends the work to the render queue/gpu, CPU starts to work on the next draw call. Since the render queue is zero, does CPU’s drawcall gets eliminated since at the time being GPU is not done working on the former frame?
If this is right, then CPU’s second draw call gets eliminated and starts to work on the third draw call, then does GPU sit idle to wait for receiving the next draw call from the CPU?

If this is the case, then how could we explain CPU’s load percentage goes lower on an extremely GPU bottlenecking scenario. Where’s the point that CPU seats idle?

Thanks for reading it.