Yes, except that China also uses its population as a military threat. It going down would take away some of the impact of that. So it always needs to go up, to reinforce it.

Mostly in the past before they were well industrialized. When you had India with over a billion people as a threat, it was a good measure. Now most of the surrounding countries have fallen below population replacement rate excess population can cause issues with economic growth in places resources and space are constrained.