Lying to reporters is not a crime. Libby would have had to testify that he was unaware that Plame worked for the CIA until he heard it from Russert (or some reporter). It is not clear that Libby actually testified to that from the indictment, but maybe I missed it. If he did, than I take your point.
That is basically what the indictment asserts - or at least that he was unaware that Plame worked for the CIA at the time the conversations in July took place. That is, he could hear a rumor from a reporter in June, check it out with the CIA in June, then have conversations in July, and later on tell investigators that in July, he had no accurate knowledge of Plame, only rumors.
Best I can discern from the indictment, Libby did not disclose his knowledge as a matter of fact (did not disclose his contact with CIA/VP/State) either during his Oct/Nov giving of statements, or at his March giving of sworn testimony. Instead, implies the indictment, Libby asserts that he learnd of Plame (in that timeframe) only by being part of the rumor mill.
Of course there is evidence outside of the indictment, and my comments are based solely on the contents of the indictment.