Yes it's a stretch to claim they came from a specific country... If you go to remote islands in Australia with nobody on them, there are coconut trees there. I highly doubt they were planted there by people. They are pretty good at surviving long ocean journeys and they can start growing above the ground, they don't even need to be planted. Probably the most hardy tree species that exists if you think about it. According to Claude, a coconut can survive 3 to 4 months at sea. They could have come from any beach.