Because there are rumours Chinese want her back in China, and not to spend herself in long Turkish seasons, for Tokyo 2020. I heard they even tried to buy out her contract this off-season, but Vakif refused.
None of rumors came from credible sources. some chinese media/people like to make up stories and spread over the web for whatever intent. any sensible person can see the issue with team china is not about Zhu, but the subpar performance of her teammates. Pulling Zhu back to China from the high level competition will be such a deplorable short-sighted action and never a real solution to the problem.