Google "Interesting Finds" on Mobile SERP

Does anyone have theories for how Google's algorithm selects articles/pages for "Interesting Finds"? For those who don't know, "Interesting Finds" is a grouping of 4 articles/pages featured on a Mobile SERP. It only appears on certain search queries.

One example of a query that shows "Interesting Finds" is seo services

Try displaying a small amount of content, 100 words say, that covers something that the other sites don't. Display on it's own, under it's own header, a bit like you were trying to get the featured snippet.