This is basically a rationing system, like the olden days in China and the Soviet Union, where it wasn't enough to have money, you also needed a ration coupon to buy the good. Everything was rationed not just food, but bolts of clothes, consumer goods of any type, electronics (if you were fortunate enough to be able to afford it).
In this way the regime controlled scarcity and ensured loyalty and favoritism by awarding special rations and coupons for those who uphold the correct ideology and "meritorious labor". Each month your work unit issued a new ration book for the month that is based on your families' allotment of grains, cooking oil, clothing, soap, etc. If you are being a bad boy and you don't get your ration book for the month, you can't buy the goods in the state supply shop and have to go the black market.
Thus pure money wasn't good enough to live well or even to survive in those systems - one needed connections and access and the authorities can cancel your access at any time.
That is what a CBDC has the potential to evolve to and what worries me - a digital ration book. If all a CBDC is is digital cash, then we already have that system (Visa, e-payments, etc) and things won't change much but if a CBDC is a programmable form of money that can be disabled, inflated at will, turned off, or only allowed to buy certain goods - then there is no limit to the amount of tyranny that will be on hand. In a free country common people will not and should not accept it.