That's true of every game, and taking that view, this thread wouldn't exist! For understanding game rendering tech on these boxes, looking at the rendering resolution is a big factor. Hence for this thread, we take the rendered resolution as being the framebuffer resolution used for rendering the bulk of the opaque geometry. Otherwise it'd be impossible to get a clear position for discussion. eg. A game with the 3D rendered at 540p, upscaled to 1080p and then with a native 1080p UI overlaid, would not be a 1080p game and would not be comparable to a game rendering in native 1080p. For discussing nitty-gritty details, like comparative alpha-blended particle framebuffer resolutions, there are the Tech Thread and individual threads.
Yes, the UI framebuffer. Upscaled low-resolution UI's look horrible, and as they are cheap to render, a native UI makes perfect sense. Also note that the response says 'render targets' and not 'framebuffers'. Some of these are going to be textures at maybe 512 x 512. You can also render larger than the output resolution and downscale for improved quality, although that's expensive. The Snowblind Studios engine on PS2 did this, adding 2x supersampled antialising and creating an incredibly clean look for the hardware.
