It's using one of those annoying "easing" libraries for scrolling. I kind of hate that they break perfectly good two-finger scrolling just so they can get an "special effect". There's one reason Natural Scrolling is called Natural Scrolling: the screen is supposed to reflect what your gesture means. "Easing" only works if you introduce it as an end-of-gesture effect, not if you have to "accelerate" into it.