Below is the screenshot of my board on Pinterest. I don't understand why some pins (actually, most pins) don't have the title of the article.
Here is my analysis:
Pin 1 and 2 are the same article, but pin 2 is shared to Pinterest through Pocket app in iPad, while pin 1 is pinned directly on web. Neither pin has the title, so I guess whether it is saved by an app or not is not a factor.
Pin 2 and 3 are saved through the Pocket app, but only pin 3 has a title. This strengthens the point I made above.
All three pins are saved from one website, so I guess which site is saved is not a factor.