According to Fitzgerald seems like Cooper was that last to know.
What did Libby and rove talk about?
Fitzgerald has refered to Valerie Wilson's position as "classified".
Apparently every position at the CIA is "classified" including janitors etc.
So either Fitzgerald has determined that she was not "covert" (as in the law that makes it illegal to out a covert agent) or he thought he did not have to publicly make that determination in Libby's indictment because he is charged with lying to the Grand Jury, Obstruction of Justice, not outing a covert agent.
But there also laws governing releasing "classified information." Of course, it is done everyday and few people are charged and convicted with releasing classified information.
But it is still unethical for someone with security clearance (Libby) to release classified information to reporters (even if was the name of the classified janitor at the CIA or the former but now washed-up agent Ms. Plame.)
Thus, Libby didn't want to get painted with leaking classified information so he lied and hoped the whole thing would just blow over.
Or Libby thought that Fitzgerald might eventually determine she was a covert agent.
I hate the way REPORTERS use shorthand to tell a story that while accurate, isn't TRUE or FACTUAL.