When you sign in your bitcoin exchange and then go to your bank's website and make a "digital" transfer of fiat to that exchange you are already using "Central Bank Digital Currency" and it is easily dumped for bitcoin as long as the bank doesn't cause any problems for its users. I don't see why this should change in the future if they change the database they use for their CBDC!
Also who would want to hold CBDC when they see cryptocurrencies going up in price and obviously CBDC reaming/acting as a "stable coin"
The same reason why some people hold fiat(USD/GDP/EUR/PHP/etc) and stablecoins, and not bitcoin/crypto.
Even though both are centralized but there is still a big difference between anything issued by banks and stable coins. The former will always demand 100% centralization and KYC while the later is partially centralized and (so far) doesn't require KYC.