They are not in a busy part of the ocean, but I suppose it is to warn people away. That archipelago is not fully charted, so it is probably a good idea to keep away from much of its coast. Probably dozens of uncharted reefs.
Uncharted archipelagoes in 2026? Couldnt satellite imaging help with this? And I don't think it's near any shipping lanes theyre incredibly remote, theyre more likely there so the research vessels that enter the Port-aux-francais harbor can see the shore