It's always surprising to me when people believe anonymous government sources, when the statement is in that governments interest. Government personnel are paid to act and speak in their governments interest, which includes lying, exaggerating, provoking, etc., and in my experience when that source is anonymous and when the statement is advantageous to that governments interests it's probably not true, or not the whole truth. It lets that government publicly disavow knowledge of the potentially inflammatory statement (we don't want to hurt US relations!), while simultaneously telling the opposite story with deniability (we want our citizens to think well gladly hurt US relations!).
For all we know this "leak" is being used to legitimize something else entirely, perhaps the Brazilian military is unhappy withy the decision and this story exists to deflect criticisms from domestic sources: we picked the unpopular aircraft because the NSA would use Boeings aircraft to spy on us. Or we want to send a message, etc.
Welcome to world politics, where the truth is rarely what people say it is.