Maybe. But maybe not. Stranger things have happened in history, and they really have. I'm going to go out on a limb here with some wildly uninformed speculation, but the people running the show in the PRC aren't normies. They are people that have clawed their way to the top of a ruthless pyramid of power. Or were raised from birth by people who clawed their way to the top. Either way, they're at the top for a reason. Look at China's communist history, and you'll see a fairly consistent, running theme of systemic paranoia -- sometimes thinly-veiled, sometimes outright -- that occasionally spirals into non-trivial political purges. History is full of examples of plot twists even more bizarre-sounding than this, and I am far less certain than you are that the perceived perpetrator(s) of such a targeted depopulation event would be so clear cut to the Politburo.
All that aside and more importantly, after one really bad crop failure, the PRC will have more existential problems on its plate than who gets the blame.
All that aside and more importantly, after one really bad crop failure, the PRC will have more existential problems on its plate than who gets the blame.