This jitteryness is because the sample doesn't have antialiasing enabled (since it's pixel art) and the background scrolling is 0.1pixels per frame, which means every 10 frames it snaps 1 pixel. The scrolling is also updating on fixed amount per frame instead of looking at deltaTime, so if there are lags or small differences in frame time this might look choppy.

But I think it's more meant to demonstrate drawing parallax layers rather than subpixel scrolling.