It's not like they're utterly dependent on every part of the global economic supply chain functioning lol

I do not think it is certain China would apply it universally, a totalitarian government views its population as an enemy to be controlled. The most likely scenario is that until machines can take over production the general population would be encouraged to reproduce but no longevity treatment given, with it being forbidden to discuss the fact that the ruling elite does not age. The reason the treatment would be denied in the East and the West is that significantly increased lifespan inevitably increases experience which itself increases the likelihood of revolt against subjugation. All governments are in the business of management and not the business of improving the lot of their population, talk of improvement is just one of its methods of control. The only improvement that is permitted is technological advancements in production and surveillance.