In trying to retain their dollar earnings as the yuan stumbles, Chinese exporters are resorting to using currency swaps to manage that. According to China's FX regulator, domestic firms swapped a record $31.5 billion for yuan with banks in the onshore forward market in July.
This allows the exporters to place their dollars with the banks and get yuan instead, but through a forward/swap contract that will eventually reverse said flows and receive dollars again. It's a neat little workaround and one that is quite commonplace I would say for larger firms and corporate clients of banks.
I doubt Beijing will have the appetite to hunt down these names and force them to convert their dollars but they are trying to offset things on their own already as seen here earlier.