Unlikely any civilian could just book a flight there, you will probably need to prove you have a good reason to go there.
So either local fishermen returning from a visit from the mainland, or civilian technical specialists/consultants working on projects on the island and maybe family of those civilian techies and soldiers based there coming for a visit.
Any civilian allowed on the islands would almost certainly have been given a security brief and been asked to sign some form of NDA on what they saw on the island.
Until they build a huge hotel and actively encourage tourism on one or more of those islands, it will be difficult if not near impossible for regular civilians to just book a flight there and have a nosy because those are essentially largely military outposts and there will be a lot of sensitive work still being carried out there that the PLA would not appreciate being splashed all over the net thanks to some snap-happy tourists.