Compared to their renewable buildout the nuclear scheme is a token gesture to keep a nuclear industry alive if it would somehow end up delivering cheap electricity. And of course to enable their military ambitions.
One armed bandit says explore as well as exploit. This delta you cited indicates the pendulum currently is more exploit than explore, but its not a static equation.
TBH this part seems key, even PRC couldn't operate full western designs reliant on western industrial capacity economically, part of it was simple incompetence of western supply chains (business closures / regulatory drama / sanctions). Nuclear seems viable once you strip out a lot of the politics that makes them uneconomical, hence PRC had to indigenize the designs since once western supply chains enter picture, the schedule goes out the window.