There’s more than just these two, and also non Sino-Soviet equipment operated by other countries.
China has many options. Pakistan, Bangladesh, Myanmar, Laos, Cambodia and North Korea are ones that come to mind for me, and I know for a fact there’s more. All That while already having two Chinese nations with their separate militaries combined in a tree, one of which being a military superpower.
So why take from the smaller pool of western aligned nations that are friendly towards Japan?
Some people are still never going to trust leakers anyway even if it gets a 110% accuracy mark on it lol. Good to take leaks with a grain of salt and as a reference point but outright denying it is just breathing copium tablets at this point.