[RandomLensman]

Two dollars in the same situation are fully fungible between each other - if they are in different systems, or even gold, silver, etc. they are not in the same situation or even money or dollars (but something of a dollar value). For example, dollars in a checking account are fully fungible, you would not know which specific dollar you get if you transfer one.

That situationally swapping between fungible things can be blocked etc. doesn't mean that they thing itself isn't fungible.