(Not sure if I should ask this question here. Mod, please feel free to move as appropriate.)

When I boarded a LAX/PVG flight, I heard the GA told the passenger in front of me that he received a complementary upgrade and handed him a new boarding pass (quite a few more still on her desk). When I asked what kind of complementary upgrade is offered, the GA said let's see then told me "oh, you are in business class already". I didn't talk more to her as there was a long line behind me.

As I remember there is no complementary upgrade for international flights (E to E+, Y to C, or C to F). So I wonder if this is a change or just unique for this flight. The C had about 20 seats unassigned about 20 hours before the flight but was actually full. Interesting.