- Do 3d touch peek/pop on Explore "On this day" footer. (The footer says "More historical events on this day")
- After popping the full list of historical events for that day ensure you see a "< Back" button at the top.
Testing on iPhone 6s (iOS 10.3.3) and Wikipedia app 5.6.0 (1171). According to the screencaps below the "< Back" button shows when the article is fully opened (but not when just peeked at as shown in the first image), this seems fixed according to expected results.