Just booked an award to/from China, and the outbound flights have an odd notation on the confirmation. The outbound portion of the award is Mixed Class (economy SFO-YVR and business YVR-PEK). On the confirmation there's an exclamation point in a circle (usually used to indicate things like "Overnight Flight" or "Long Layover") with the text NON_PREFERRED_CABIN for both flights. What does that mean, and why would it be on the second flight as well, which booked into Business (I) on a two-class AC aircraft (I hope). (Unfortunately seat assignment was not offered during booking on the non-UA flights.)