I love seeing examples of short sprints like this. It's helpful to see how other teams structure their sprints and especially how they conduct the exploration/brainstorming phase.

While there are a couple of buried links to the source, I think it's disingenuous for the article not to note that this sprint follows a methodology devised and championed by the Google Ventures design team:

https://www.gv.com/lib/the-product-design-sprint-understandday-1