Glitch in the system. It remembers your status at the time the reservation is made. In your case, it helps you.

In reverse (booked when one status and then qualify for a higher status later before the flight), it can be harmful. In this later case, ask them to clear your Mileage Plus number from the record and reenter it. The system will then show your current status.

In your case, you obviously would not want to reenter your Mileage Plus number.