If you're dealing with money, you should at a minimum have some kind of ledger, and derive the current state from that.
Calling an SQL transaction "Classic funds transfer" is a bit of a disservice to all the banking that happened before databases. Mesopotamians were recording transactions on clay tablets 5000 years ago.
Using incorrect and invalid models of real world systems and using them as exemplars of technical concepts, even as a short hand, is a sign of a not well written document.
It gets worse, because the "level up" to distributed transactions builds on the model by trying to show two banks engaged in a distributed transaction using 2PC to handle a funds transfer. This doesn't exist. It's not a thing. It never has been. There's nothing "classical" about this example.
It exists in the same canon as "a manager is a person. an employee is a person..." examples to explain data modeling.
Using these "examples" leads readers (learners) to walk away with incorrect understanding that they will likely spend a ton of time having to unlearn and overcome.
Good luck with your Chesterton's Fence adventure boys. You're gonna need it.