As explained by Pinterest:
"Earlier this year we launched a chronological following tab entirely dedicated to the people and boards you’re following. In continuing to respond to Pinner feedback, today we’re launching an immersive single Pin format for easy scanning from idea to idea. And, now just one tap on a Pin in the following tab will take you to directly to the website for more information from the creators, driving traffic to influencers, publishers and brands."
For comparison, here's what the following tab looked like at launch (back in March), and now, with the new single Pin format:
Pinterest says that the option:
"...gives Pinners control, as a platform where you can truly toggle between experiences - whether you want chronological or not, algorithmic recommendations or not, or a mix."
Original source: https://www.socialmediatoday.com/