The accumulation of essential commodities by China is seen as a diversification away from holding the US$ into specie that will probably go up in value, hence it is merely a divestment and preference for a better investment.
But there may be another reason. As China has learned, it is very open to invasion. Having adopted expansion through invasion into Sinkiang and Tibet, it has gained strategically from this policy. Formosa is a tougher proposition as it is an indepemndent country overrun by Republican, openly capitalistic chinese after the second world war. It is also guaranteed by the west as a means to keep China under control. Strategically China is surrounded by non-allies or past enemies. With the two invasions it should have all the living room it needs even with the one child policy.
Stockpiling is also an historical prelude to war. The USA is engaged in topping off various strategic stores the most important of which is oil. Oil is Mastery. Solar powered jet aircraft are not yet on anyones military agenda. China is deficient in oil, apparently. Singapore is a strategic crossroads for sea traffic to China. The idea of Anthropogenic Global Warming is a device aimed at limiting Chinese energy generation, to strategically cripple further expansion. It is easily seen through as a ruse and believed only by those duped by western media. Where is China to get the oil needed for modern warfare?