I really don't think this will be policed at all, ultimately they want the dollars.
I also don't see how they can track it. My UK bank account has nothing to do with Argentina and is registered to my UK address. Also, in the UK, there are no ID cards or anything like that, so there is no ID or passport number linked to my card. I've "accidentally mistyped" my passport number for online purchases here and it all went through fine.
Does anyone know any good Visa cards for low foreign transaction fee? So far, the Wise rates haven't updated and most UK banks charge 3% for foreign currency transactions.