Well it's similar. I had a look and they basically tie the entire state of the page to the scroll position, but quite a lot of the page just scrolls normally.

Well it's similar. I had a look and they basically tie the entire state of the page to the scroll position, but quite a lot of the page just scrolls normally. So while they do use the position on the page they're not trying to override the default behaviour, they just add to it. The only real change to scrolling behaviour are the few elements that remain in screen for a short while, which is fairly nonintrusive, and doesn't really feel unfamiliar (although it might have if they didn't cleverly overlay a few boxes that scrolled normally).