On a wide window the picture and description in the margin stay beside whichever rows are on screen, rather than sitting at the top of the section and scrolling away from the rows further down. It settles near the top of the window and follows the list from there, and stops at the end of the section, since the next section's margin is about a different set of rows.
Keep the front page picture in view while you read the list
The picture in the margin now travels down the page with the rows instead of staying at the top of the group.