You're not missing much imo:
or maybe their intent was to bore me off their site because I'm not a journalist. In that case they did well!
It's unnoticeable when not using smooth scrolling (my personal default). Not a huge problem for a design feature to be unnoticeable though.
When smooth-scrolling using the middle mouse button on Chrome/Linux, it doesn't update dynamically as it scrolls; the background snaps into position when scrolling stops. In Firefox/Linux, it does update dynamically with middle mouse smooth scrolling, but jerkily. It's noticeably bad in both browsers.