I don't think that's necessarily true - from what I've heard, Yale and Duke both continue releasing acceptances into March. I'm wondering if it has something to do with how early you submit your application (even though they're not technically rolling admissions...).
I also heard good news from Yale on Jan. 24, and from Bren about two weeks later. No funding decisions from either school yet, and no word from Duke so far either. It sounds like these schools all over the place time-wise in terms of releasing admissions decisions!