I remember being surprised the first time I saw this "feature", which was with my own startup's recurring charge on a credit card that was replaced with a chip card. I didn't understand how the charge had gone through, since the new card had a different number, and I was sure I hadn't updated it in my startup's payment system. I called the credit card company and they didn't know either. When I contacted Stripe (my payment processor), they were able to explain what had happened. I can imagine that people who encounter it in less-controlled situations would be even more confused.