Who the hell is talking about a blockade?
Blockading the PRC is an act of war. We are not nearly to that state yet.
Japan was not blockaded - it was embargoed. Nobody in the US was allowed to sell them scrap metal or oil. Japan didn’t have metal ore or oil so that threatened to destroy their economy. Their options were to change policy or find other sources.
No one is talking about a blockade at the moment, but that seems to me to be exactly the possibility the CCP has in mind if it is stockpiling. Same as Japan in 1941.