Exec 1: So, should we tell the world about The Flash?
Exec 2: Our new TV show out this month or the one in theaters years away?
1: The latter.
2: Sure! Then, we'll tell the world later that the role will be played by Ezra Miller. That way, we can let the TV show do its own thing, then next year give Miller a proper introduction at Comicon, where he can do interviews and talk about the role. It'll be great! We're obviously in no rush!
1: How about instead we simply drop his name as The Flash in the middle of a press release, giving him the least amount of fanfare imaginable and potentially confusing the layman regarding the TV Flash versus the film Flash?
2: That sounds great too! Let's do that!