Central Bank Digital Currencies are being implemented exclusively on systems that allow the "Central" authority to absolutely ensure that nobody except that central authority can control every transaction in those ledgers.
And I don't think you meant the "C" in "Currency".
Thanks Pjkundert, you're correct I should have said 'first C".
What I meant was that it was ironic that CBDCs are being constructed using systems that use blockchain, i.e., centralised systems, designed to deliver centralised currencies, based upon technology exclusively designed to deliver decentralised currencies.