If they want a digital currency, they can do so in a centralized way. Doing so has no need of a blockchain at all.
The purpose of the blockchain is to provide a decentralized consensus among the users.
It stops counterfeit money.
You aren't paying attention.
The purpose of a blockchain is to establish a decentralized consensus.
A government operated digital currency has no use for decentralized consensus.
A centralized digital currency without a blockchain stops counterfeit money just as well as a blockchain based one.
Please take some time to learn a bit and ask some reasonable questions before making assumptions about things you don't understand.
I won't be repeating this again here.