The article gives both description and photographic proof of the contact with the sentinelese people.
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.