It's a great question, one I've wondered about before, but I'd have to say that the answer is: "not literally," or at least "not entirely," because it would crash right through the fourth wall as it seamlessly makes its transition into the closing credits. That transition begins with a ritardando of the "Throne Room" music, so it can't be convincingly argued that you're supposed to make a cut out-of-universe precisely when the end credits start. The transition would have to begin at some point before, during the ceremony.
Looking at the other end, with the way the music begins with the fanfare, it very definitely does seem to start out diegetically. But by the time they've gone up the stairs and are waiting for their medals, I've given up trying to maintain the belief that it's in-universe and accepted that the music is a regular musical soundtrack.
