Good point, you're right (and btw, that's a crappy result from Bing!). As a verification, I did another experiment:

https://www.google.com/search?q=usa+scientists

apparently gives results from the same knowledge graph and displays them under the same heading, but orders them differently from:

https://www.google.com/search?q=american+scientists

So apparently Google, while understanding the search query, still orders the results by the words used to express it- and in the second case clearly privileges African-Americans because of the "American" substring. My bad.