1. The author's meeting with the Sentinelese.
2. The author's meeting with the Jarawa.
You are correct that most of the photos are from the meeting with the Jarawa and that much of the article describes the author's time with the Jarawa but there is a segment which explicitly describes the meeting with the Sentinelese, separate from the Jarawa meetings.
The only reference I can find for such contact is a blog post and a 1993 news article that appears anecdotal. I'd like to see the journal article written about this contact by the Anthropological Survey of India which funded the contact with the Andaman Islanders, but I can't find a source, leading me to believe it didn't happen as described.
The best I can find is this book: https://books.google.com/books?id=-4PDCQAAQBAJ&pg=PA140&lpg=...
This text claims to have made friendly contact in 1986, and says 1994 had contact on the eastern coast.
These dates don't line up with the story, and I can't find any official source information about the contact, so the inconsistency is a red flag.
I don't know how one would go about researching Indian anthropological expeditions to find the officially-documented connection to reality, but presumably that's where you'd start, if you wanted to verify the story.
I don't think this is contact with the Sentinelese, but with the Jarawa, another tribe on the same chain of islands.
The photos here appear to show contact with a Jawara tribe, and are incorrectly labeled as Sentinelese.
If the Indian government just sent people over to throw coconuts onto an island and didn't have any official documentation of the trip, or research that the trip resulted in, a story about it more than 20 years later doesn't hold a lot of weight for me.
As you can see, this is just me being a bit pedantic, so if others want to take this as a source of truth, they are welcome to do so, I'd just like to know why they think this is authoritative.
While in theory a similar looking beach could be anywhere, and the native people could be of any tribe, in the first photo the visitors are standing in water, offering coconuts. The other tribes live in the mainland of Andaman island, so when meeting them you would more probably arrive on foot on land.
This is some, perhaps indirect, indication that the visitors arrived on a boat, and the photo really is from where the caption says it is.