Not at all unusual and many airlines around the world ask to confirm the CC used upon check-in.

With that said, I have never had this happen when flying domestically. With international, just a couple destinations. Most recently to the Dominican Republic. DL seems to consider it high risk for fraud...whereas AA does not, and I always use the same CC when booking on either airline. Oh well, I don't use a CC I don't carry or choose to leave behind at home...so it's not much of an issue. It only becomes an inconvenience if booked for another person I suppose.