Its called "settlement" when its final. You probably dont need that ever or dont even know there is a difference between a payment and settlement but financial systems do know the difference very well. They just hide it from the end user. Settlement is the actually difficult part the rest is just moving numbers around. After all fiat is mostly digital.

And BTW no we dont need bitcoin for this at all its depreciated tech. But other DLT can be very usefully. There is a reason CBDCs are a huge topic in global finance.