This examples don't mean the dollars aren't fungible only that where they are stored can make them less accessible or subject to fees. Its like the difference between a gold nugget in your hand and one that's buried deep in the ground. The gold itself is inter-changeable, one nugget is worth the same as the other if side by side. Only one is in a more inaccessible location and you'd have to pay the cost of retrieving it. If you magically switched the two nuggets, the situation would be exactly the same from a value perspective.