Regardless of whether the mines are outside of China, the refinement/separation step of mined raw materials is done mostly in China (>80% global capacity). In addition to the 3-5 year lead time of building the capacity through new refineries, there’s a significant process optimization learning curve (non-transferable learnings) to move down the cost curve for new refinery entrants.

On central planning, this is well known that China manages raw material prices according to the 5-year plan: https://www.reuters.com/article/us-china-commodities-idUSKCN...