I don't understand - how is the custody even part of the payment system, though? For example, if I keep all my money in the bank, then cash is only as reversib

I don't understand - how is the custody even part of the payment system, though? For example, if I keep all my money in the bank, then cash is only as reversible as my bank account is solid. But "cash as a payment method is reversible, if you store the proceeds in a bank account" is not a statement that tells you anything about cash, it's a statement about my bank account. It would be a solid article if it attempted to argue the point it proves, which is that "there is no such thing as unseizable". But it doesn't, so it isn't.