If they're going to make that many bikes, why not just give them away? Why have them be "shared" and made to be returned to a pile?
It would at least eradicate theft. Most people would have the same model. You could get a handout instead of having it stolen, and if it was stolen, then that person could get the handout. And the only people claiming them would be the ones using them.
In practice, China is highly capitalistic as an economy. It's authoritarian capitalism, not communism, even though it has a "communist party".
This phenomenon of bikes piling up is literally venture capitalists throwing money at startups (in return for equity) to deploy more and more bikes to outnumber competitors in a hopeless race to monopolize bike sharing. It's literally an exhibit of one of the failure modes of extreme capitalism.
Giving them away, as GGGP suggests, would actually be a departure from capitalism, and perhaps a good one.
It would at least eradicate theft. Most people would have the same model. You could get a handout instead of having it stolen, and if it was stolen, then that person could get the handout. And the only people claiming them would be the ones using them.