It would be silly for central banks to not be accumulating some Bitcoin just in case. They understand how money works..
they are not fools, they are afraid of losing money, bitcoin has an anonymous creator, bitcoin is decentralized and can be manipulated. We are talking about increases from $ 6000 to $ 20,000 and subsequently a price drop from $ 20,000 to $ 6000 in a few months, this is a very dangerous investment and central banks would not risk investing in something like that. One day they will be able to invest in bitcoin, but only when the bitcoin volatility is not too high.
In reference to the topic, central banks are not controlled by governments. And functions independently.
In my country where corruption is very high, the governor of the central bank is appointed by the president of the republic and the president of the republic can dismiss him whenever he wants and in my country the central bank is controlled by the government.