I highly doubt it is made in China. It is very likely that the author of the article is trying to stir up something like "every 'evil' deed has Chinese behind".It seems will be manufactured by China .. well China is just the manufacturer and the owner is Belarus
China does not want to send weapons to an ongoing war if Belarus decided to use Polonez M for real. Neither will China see her client run out of ammunition when needed. The solution is simple, have the client capable of building it. There are planty of examples, such as Iran's anti-ship missiles and Turkey's M20 which is Polonez M. Hypothetically if Cuba has the industrial capability, they may build it locally as well.