Building before the Pearl Harbor attack, Japan was rolling out aircraft runways on "worthless" Pacific islands snatched from Germany after WWI.
I think this is just muscle-flexing by the Red Dragon.
There's almost nothing to be gained by starting a hot war with most of the civilized world. China would be reduced to rubble in pretty short order and even if they "won," they'd be pariahs on the world market, so their economy would collapse.
It makes a lot more sense to remain peaceful and milk the Western idiots for all they're worth.