Reading all kind of CBDC propaganda and those who are clearly against CBDC I absolutely can't get something real from that stuff.
Every single feature/option/whatever of CBDC could be implemented using current bank card/account system without single problem. Everything, from any restrictions to programming buying power or whatever. Every single thing that somehow connected to CBDC in everything written about it and posed as threat/advantage by whatever side is a question of a few minutes scripting in bank computers over current card/account system.
So, what is the real point of pushing CBDC crap by TPTB? Money laundering? Creatiing a base for some other narrative unknown yet, like kind of cyber threat fearmongering? What else? Anybody?
Singular currency could have sense only if most of the world is under the control. You can't create singular currency if nobody except few buddies agree to use it.
And again, there is no any technical problems to tie your card/bank account to all that UBI/SocialCredit/Metaverse, whatever and use that extended info in transactions to alter sums, limits, rates, taxes as they wish. And they have it right now without any CBDC.
I could imagine that there could be a singe worldwide CBDC with different local names but with shared blockchain, and that was one of my first guesses, but you need a unified world first.
Your last paragraph is exactly what I think they're doing. Shared blockchain, but different named CBDCs on the front end.
But it is senseless while there will be countries with cash. It will be relatively easy to just use the other country cash if your own country will get rid of it. There will appear a lot of gray/black exchanges where you "buy" something with CBDC in another country and immidiately get foreign cash from moneychanger. Then use that cash as you like. Another person who get that foreign cash could do the opposite - "do some service for a foreigner" along with giving cash to moneychanger and get CBDC.
This is one of the biggest reasons, I think. This is their plan for the One World Govt. They've had practice with oil and USD. The world is already unified, they're just erecting the columns, and the first of those is CBDC.