Okinawa has traditionally been culturally and linguistically separate from Japan. It wasn't until the late 19th-century that Okinawa became part of the Japanese Empire.
That history is reflected in the structures of this world heritage site. The nine sites which are included in this property all harken back to before it was absorbed into Japan.
I've often said that the Ryukyu Islands are Japan's Hawaii. A chain of islands annexed in the 19th-century with their own culture, and now people go there for warm weather vacations.