My point is that, based on the clip, it's almost impossible to tell exactly who is lying there on the ground. Unless you've read the books, there's almost no way you can't tell (for certain) whether it's Fred, George, Bill, or another Weasley (Percy, Arthur, etc.). And, as I said, while the event is heavily implied it's by no means made explicit by the very, very brief clip. Put simply, making a big fuss over the incident -- because you know, from reading the books, exactly what it represents -- makes it far more of a spoiler than it otherwise would have been. Take, for example, the trailer for ROTK. There's a shot of Eomer grieving over a blonde-haired person followed by a tagline: "There can be no triumph with out loss." If you've read the book, you know exactly what that shot is referring to. If not, it's somewhat open to interpretation. Same for the DH2 trailer. It's obvious if you've read the books ... but open to interpretation if you're completely spoiler free.
