That's what I thought too. I could see how reading fiction could make you more empathetic, but I'm not sure how it helps you read people's facial expressions.
I think it might have something to do with people reading fiction and visualizing the characters in their minds, that we conjure up facial expressions for characters in books when there are lines that say "he sneered, he smiled, he frowned, she laughed, she ogled, etc.".
This was a good one! Looks like they are photos of people "in the wild" rather than posing/acting out emotion, which makes recognizing the expressions more about trying to imagine what people are feeling behind those eyes and less about going down a checklist of which muscles should be contracted under which circumstances. Also, the possible descriptions were mostly of complex states like "pensive" and "concerned" and "preoccupied" which is what most people run into most of the time, rather than exaggerated/un-nuanced things like "afraid" or "happy".