Google appears to be conducting another experiment with its Search results. The top stories section is showing a secondary box underneath the featured news articles containing a link to another story that provides more context on the same topic.
The new feature is called "For context", and it highlights a related story from the same source as the primary news article in the Top Stories carousel. It appears that the goal is to provide readers a broader insight into a particular subject. The latest change has been spotted by a Twitter user, complete with some screenshots of the featured articles alongside their secondary stories.
At the moment, it looks like the "For context" section is limited in availability, as noted by Search Engine Roundtable. It also seems that secondary links do not show up for all articles in the carousel, with no official word from Google as to what articles need supporting stories (via 9to5Google). This suggests that the new feature is not applicable to all topics.