I think especially since it's Microsoft, Nintendo can get away with it, because no one really doubts Nintendo handling their own IP. Especially with Fable after Legends. I'm already sure Fable IV will be polarizing, so it's probably best for Microsoft to be as clear as possible how it's going to look and feel when they finally show it, so we don't get just two years of people ripping in to a title card and some concept music.
Not that people won't rip in to it regardless, because people love to hate, but at least once they've shown it, they'll know the people ripping in to it aren't their target audience, and people won't be able to build 1000 pre-built assumptions like they did for Carckdown 3, which wasn't great but reviewed worse than it deserved, mostly because of how early it was announced.