The Beak and Barrel will be open by then. So definitely can’t wait to reveal news on that till the event.
I think with these types of things they may be getting the news portion out first because we’ll see the concept art, props, or even ride vehicles, like the Buzz Lightyear one, on display at the event lobby. And instead of a free for all barrage of blogger posts and lack of context from people flooding to report on it all at once at event start, they can instead control the narrative well in advance and even create hype. So now when we enter the lobby and see these things on display we can just go “oh cool” instead of “oh I better report this asap breaking news”.
But that’s just a theory.
Destination D23 is not usually for announcements. The only reason it was a couple years ago is cause they needed a do-over after the ill fated bluesky D23 Expo the year before. But usually this is a fun fan event for history and not really a place for Apple keynote style reveals.