I (practically) designed this. Related pins are the highest performing parts of the closeup view on Pinterest. Before, they were far below the fold and by making them more prominent, you increase engagement by (IIRC) double digit percentages.
I love how these types of decisions are made based on metrics ❤️. On the other hand, I'm more into focusing on the pin I'm on, I don't know, I'm from the tumblr era hahs