The top row of Knowledge Graph results, according to Chitu, appear only once you click on a new "explore more" link that appears in the side panel Knowledge Graph results.
The test was running yesterday, as evidenced by the Amelia Earhart doodle present in the screen cap. It's not clear how many users are actually seeing this. My guess is not many. Google, as it will often tell us, runs numerous experiments all the time, and ordinarily, they are to small sets of users.
Matt Cutts talked earlier this year about how Google runs 20,000 search experiments a year. Many of those, obviously, never see the light of day.
All of that said, Google has expressed a great amount of enthusiasm about what it has done with Knowledge Graph, so it would not be surprising to see them play it up even more in search results. The company seems to view it as one of the most significant things they've done for search in years. Google considers it to be a step away from keyword-based search. "Things, not strings" they like to say.
With this kind of mentality, it could make a great deal of sense to put such an emphasis on these results, right below the search bar, and ahead of the traditional search results. It really wouldn't even be all that surprising if they did this without having to click the "explore more" link. Of course, doing so could ruffle any number of feathers among the crowd of antitrust complainers, who would likely only see it as Google promoting its own product (despite the data actually coming from a variety of third party sources (most notably, Wikipedia, which is often the top organic result for such queries already).
It is looking, by the way, like Google is about to make some change to its results in Europe, as a settlement with the European Commission regarding antitrust matters.
It's also questionable whether the majority of Google users would prefer this approach to search results. After all, Google has gotten to where it is today without such a layout, and historically a sense of simplicity in design (which seems to be withering away in recent years). Google always claims to put the user first, so I'm sure they're studying any feedback from this test very, very closely.
If feedback is positive enough, and people click around on the top row of results a lot, who's to say they wouldn't implement the layout without the link?
Image credit: Alex Chitu