In reference to the topic, central banks are not controlled by governments. And functions independently.

And yes they do understand how many works, and they are more than welcome to buy as every individual or organization is.
I don't quite understand what you mean by '...just in case'.
Maybe you are implying they are storing up just I'm case cryptocurrency suddenly explodes and becomes globally adopted. So they can have a certain degree of control.
There are already large investors, even individuals with tons of BTC.