The bank advocates that you swipe your card maliciously, or cash out with definite evidence. Sealing the card without evidence is a breach of contract and can be brought to court.

But if you don't repay, you have to bear the relevant interest and late fees. This is a legal relationship with the card seal, and there is no necessary connection between the two. You can't use the card seal to counter the repayment demand of the other party.