Their three island chain policy is mostly secured, in theory, by their A2/AD (anti-access area denial) strategy of land based anti-ship cruise missles and sea, air, and satellite ISR.
But yes, I agree that the ethos that underpines their perceived need of A2/AD is also what partially motivates these kind of moves.
Well, that and their inability to recognize that one the main factors of American power is our alliances, and ability to apply softpower pressure and true alliance benefits to other nations. We don’t just ram our ships into there’s to literally beat them into submission.
This doesn’t mean that the dark parts of American neo-imperialism don’t exist and aren’t real, they do and they are, just that you can’t be all bad bully all the time and still maintain those kinds of alliance based power structures.
At this point, all of their neighbors hate them. Not like how South American governments dislike the American government, but really really hate them. Many are building up their militaries and reaching out to America to strengthen their alliances, in anticipation of further Chinese aggression and expansion.