In the mentioned example (by Wix), and apart from the fade-in/out effect, there is a different and unique position-change-effect (slide-in) for each block in a given column/row within the grid. I think then if we want to re-engineer this behavior (even using individual blocks in a group layout), is to answer how can we, on a grid-like layout, create such a liquid animation (regardless of the scroll speed).
In my opinion, this is indeed a mockup as combining multi-effects (1.fade & 2. slide-in) action (on-scroll) on a single grid/list (in a repeater or not) does not seem possible.