If I'm China, and I'm dealing with a US President-Elect who has decided that the One China Policy is suddenly negotiable, I'm going to immediately throw a bunch of defensive weapons systems all over the Spratlys, too.
Trump rolls back his Taiwanese gambits: you take down the CIWS and hide them in the warehouses for next time.
Trump refuses to roll back his Taiwanese gambits: you act like you own the South China Sea, point out that the only other claim is that of a genocidal madman, and draw attention to the hypocrisy of the United States and the Caribbean.
We've long known China intends to own the waters around Southeast Asia. They've just calculated that now's the time to make their play. I think they've got it.