Yes and it's great that China is now successful in narrowing the gap, but there's an obvious historic materialist and dialectical line of critique against this argument: this would be in arguing, that the gap was not just despite the overall rapid development, but the development was in part only this rapid because of the gap. The Hukou system split the working class: Almost three hundred million people still earn less than half of that which the privileged part of the working class earns, often live in cities yet do not have the right to stable permanent residency and have less access to schools, universities, public housing, pensions and health insurance. That created a flexible and cheap labor pool, reduced the fiscal burden on cities, increased profits, capital growth and investment. These are all things that contribute immensely to growth. So rather than arguing that the development was not rapid enough, one could ask wether it really had to be this rapid, or if it was really necessary to do it this way. I don't know, maybe the answer is that it was necessary, considering the threat from the empire.

Edit: I held back with these thoughts earlier in a thread with libs, since they would misunderstand it, but thought I'd share since we're amongst ourselves now.