In that sample the foreground scrolls perfectly smoothly for me, but the background looks jittery. This indicates to me that it's not a platform issue at all. That sample is just doing something weird with the background.
But I think it's more meant to demonstrate drawing parallax layers rather than subpixel scrolling.
Update: Although, having a closer look at the scene, I see its pixel art, so I bet the author is snapping floating point positions to a pixel point to prevent sub pixel blurring.
Another small update: I was sure requestAnimationFrame was locked to 60fps, but I noticed on Chrome the other day it was 144hz, the full speed of my monitor.