Does it? Russia has 1/10th the purported population of China, lost most of their military aged men in a conflict that has exposed Russia's supposed military might as a work of fiction and yet the west remains scared senseless of Russia because of the nuclear threat. China has nuclear weapons, whether they have 10 million or 100 million men they can send to the frontlines to absorb bullets is irrelevant to their national security.

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.