For one that's not entirely true. standard windows gui calls are backed by a shared surface and accumulate drawing instruction on the system side of the render surface,managed by the cpu render pipeline, so that they can keep a dirty rectangle list and only update the dirty areas of the gpu side of the shared surface. From there composing runs on the gpu.
Then again the issue is the focus of rendering at 120fps.the rendering context should be paused between the vast nothingness that happens in between user keystrokes, that happen at something like 4kp, and in burst.
The insistence on 120fps is the issue here, not the rendering pipeline.