Peloton includes options to share workouts to Strava and Fitbit after the class is completed. On September 1, it was just a text entry about the class. Now, it includes a screen grab from the actual class.
The above photo is my entry from September 1, and as you can see, it includes just basic information about the class. Strava is where I have all the runs stored from 2010 until I started riding Peloton, so I like being able to push my rides to it to have a “lifetime” look at my fitness. I have a number of friends on Strava that aren’t Peloton users, so I like to show them that I am making good use of the bike.
On September 2, it swapped to the full image.
It appears to be something that Strava has added on their end because other apps now that a similar screenshot on Strava. Either way, it gives it a more interactive approach for your friends who are on Strava.