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.
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.