EditorialGuy - 2:07 am on Aug 8, 2013 (gmt 0)
I think it's too early to draw any conclusions about Google's "In-depth results." The examples are just examples, like the first examples of Google Authorship "rich snippets" (which featured photos and bylines of people like David Pogue of The New York Times).
I wouldn't be surprised to see "In-depth articles" results in SERPs on all kinds of informational topics. That won't happen overnight, though, because it will be a while until there's a critical mass of in-depth articles with schema.org markup.