Zimmer said this in an interview when "BB" first came out, so I don't know what you're saying "BS" about.
It's common for film music composers to create various themes/motifs for a film at the beginning to create a stylistic template for the rest of the score (and also for the director to ask to have them changed or re-worked.) Zimmer could've very well created a full-blown heroic theme from the get-go, only to have Chris Nolan ask him to tone it down and/or not use that exact version in the film. (It's the same approach that they took for "Casino Royale" -- since Bond was just starting out, you don't hear the full-blown Bond theme until the end credits -- you just hear snippets of it during the movie.)
And for you guys who are insulting the theme that starts exactly at the 1:46 mark in the trailer... um, are you deaf? You are aware that this is a heroic version of the Zimmer "Molossus" theme that was used throughout "Batman Begins," and was used over the end credits, right? However, this "trailer" version of the theme wasn't heard in the final film, so it's possible that this may turn into the actual "Dark Knight" theme. If so, that's great -- it's properly heroic and powerful.
I swear, some people like to complain just to prove to their 15-year-old buds that they're "kewl." If a movie showed a daytime shot, these guys would be saying "the sky is too blue!" If it showed the ocean, some fanboy would say, "the ocean looks too wet!" Good grief.
-- Admiral Nelson