Obviously it is a counterfactual but no serious leftist would say that China without market reforms wouldn’t have eradicated poverty, and moreover done it faster and more completely. The seeds of poverty alleviation were planted during the Maoist era; improvement in health, education improvement, and industrialization.
I guarantee that you would be cooking up these conspiracy theories regardless of any investigations that China had allowed. They could have shipped every citizen of Wuhan straight to your house so you could personally interview them and it still wouldn’t be enough.