Memes

To get terminology out of the way, they are building towards Communism through Socialism, ie an economy where public ownership is the principle aspect of the economy. In other words, large firms and key industries are overwhelmingly publicly owned, so the Bourgeoisie doesn't have power over the state.

Now that terms are out of the way, you're correct, China does have billionaires. Even though that number is decreasing in recent years while working class purchasing power and wages are rising, that isn't enough of an answer as to why they still exist. Billionaires represent a contradiction the CPC must resolve. But how is the best way to go about that? What time scale? The CPC's role is to gradually resolve contradictions within Socialism in favor of the Proletariat in any inter-class dispute. They have to erase the foundations for billionaires, not the billionaires themselves.

I recommend checking out China Has Billionaires. The important thing to understand is that contradictions exist in all systems, and it is the process of working out these contradictions that provides room for advancement.