It is not needed but there's no harm in doing it. In my case, I sent photos without annotations with my initial I-751. I received an RFE and in my response to the RFE, I included photos with dates, captions, locations, and if it was a group photo I wrote who was in the photos with us. If the photos were vacation photos I included copies of the plane tickets and hotel bookings. I also sent social media posts with my response to the RFE (something I did not do for my initial I-751), I sent social media posts of us as a couple and made sure they saw the hundreds of likes and comments from friends and family. I know it wasn't needed but figured it would show that we were a legit couple who was very open about our relationship on social media.