Given that they live on an island, I'll bet they make use of all sorts of materials that wash ashore. Even a torn plastic tarp is very useful compared to having to make one by hand from some plant material.
So culturally they are likely completely isolated, but likely very aware of the changes going on in the world outside their island.
This one is also quite nice I found: https://en.wikipedia.org/wiki/Uncontacted_peoples
> Uncontacted peoples, also referred to as isolated peoples or lost tribes, are communities who live, or have lived, either by choice (peoples living in voluntary isolation) or by circumstance, without significant contact with global civilization.