Perhaps...but when I look at the 'cow's tongue' it seems to contravene all laws surrounding proximity to continental shelves. If we are going to look at 'ancient historical claims'...well, China can kiss goodbye to itself; Mongolia owns most of it all the way west to Hungary. They may in turn run up against the Italians and the Roman Empire. Then there's Norway and those troublesome Vikings...
I must admit I am not well versed in international law. I know that China officially received the surrender of SCS islands from Japan in accordance with the ww2 surrender documents signed. As I understand, historical basis is one of main precedents in deciding many past island disputes by international court. UNCLOS provides legal basis and guide to mainly deciding eez and territorial water. UNCLOS has no jurisdiction over sovereignty dispute of islands. I wonder what basis philippines and vietnam have in claiming SCS islands if they don't use historical basis? It would be curious to know what basis europeans have to claim Americas, Australia, NZ,...; and US claim over Hawaii, British over Diego Garcia, Falklands,...
My read is historical basis is used in cases where no better or practicable basis is available like international agreements such as the legal precedents that exist today. Surely europeans could not be asked to return Americas, Australia, nz,.... to the natives of the places bases on historical basis.