I'm having trouble seeing how his argument doesn't apply to every other currency that exists, and feel like he's ignoring that if you want to pull money out of

I'm having trouble seeing how his argument doesn't apply to every other currency that exists, and feel like he's ignoring that if you want to pull money out of the cayman islands to spend locally, there is likely to be some hassle, delay, or loss of anonymity involved. Surely an economist understands opportunity cost? Is there more to his argument that I'm not seeing?