This isn’t what China does though, the moment new tech crosses the border they reverse engineer and start producing it locally. IP protections are meaningless there. How many times does this have to happen to sink in?
Keeping them dependent upon you guarantees that they never surpass you and that you can milk the relationship for all its worth economically and geopolitically. When they have their own fabs spun up it's possible that you are the one eventually stuck with inferior tech, and you lose all sort of revenue + leverage you'd otherwise have from the relationship.
It make sense. China had X amount of demand. If the demand is met they are satisfied, if the demand remains unmet they seek alternatives. That seeking of alternatives primarily means huge amounts of money, that would go to Nvidia, going to direct competitors of Nvidia to "chip" away at their competitive advantage.