South China Sea claims as conquest by civil engineering

Why are China's South China Sea islands treated differently from British and French overseas islands?

Because they are newly engineered outposts used to extend territorial claims, a strategy compared here with ancient frontier walls.

China's artificial islands differ from the inherited overseas territories held by Britain and France. The policy is described as conquest by civil engineering: build a permanent feature, occupy it, and claim the surrounding space. The Great Wall of China provides one historical analogy. Hadrian's Wall and the Antonine Wall offer Roman examples of construction defining and civilizing a claimed frontier. The method is old and currently effective precisely because physical works are difficult to reverse without escalation.