The question is, is President Xi willing to risk military conflict to enforce whatever new lines he draws on the map? I don't think he is. As we saw the air zone China drew that overlapped Korea, Japan and Taiwan, it was promptly ignored by all countries and when the US stealth bombers were flying China was silent.

An actual combat that results in Chinese loss would be detrimental to the continuity of Xi's party and the Communist Party itself. The risk is far too great for the small gain it gets. Chinese leadership operates on a cost/benefit analysis, I don't think anything has changed.

So the only logical conclusion is that Xi, along with his anti-corruption campaign to take out his foes, is using brinkmanship to further his popularity and distract people from internal problems that could lead to massive unrest. Economic downturn would certainly be a threat and war drumming has been a common political tool used by many different countries at different points in history.

A military conflict that would be launched by China so far away from it's coastline makes no sense where US has dozens of nearby bases in different countries and logistic support on it's own and from host countries to sustain a prolonged naval warfare. If there was a war, China should pick it's coastlines where it has anti-access/area denial weapons (allegedly) and opposing force would not risk their assets. It would be a nightmare in terms of logistics for PLAN if they did launch some provocation so far away from the mainland. The island building is a clever way to provoke without risking it's military.