This is kinda cool. The author decided to try and create depth in a design system without using any drop shadows. The trick? use varying amounts of contrast to denote depth, with things in the background having less contrast than those in the foreground. It’s well worth a read.
On mobile, the cards stack on top of each other.
Which has also been confusing for some folks. The thinking is: cards are always excerpts. The stacking (and thus hiding of some text) says: click/tap this to keep reading it.