The [1] parallax tilt effect was out there for some time, so I don't think FB have implemented something new.

[1] - http://wagerfield.github.io/parallax/

There is no parallax effect (AFAIK), the Paper's innovation comes from using stilt to scroll through the photo thus leaving the swipe gesture available to flick through pages/cards

Sure, but however - you can check the link; the plugin is about parallax on desktop, but there's tilt on mobile, which I think is pretty the same as on the FB Paper video. My thought is that it's not something totally new as UX.