He does know. It's implausible that he doesn't.
But he can't reveal whether Plame has or did have covert status, because that would be a violation of the Intelligence Identities Protection Act.
Saying that Plame's position was "classified" is not a violation of the Intelligence Identities Protection Act.
"Covert" and "classified" are two very different things under the law.
He does know. It's implausible that he doesn't.
Then explain his statement: "I will confirm that her association with the CIA was classified at that time through July 2003"
But he can't reveal whether Plame has or did have covert status, because that would be a violation of the Intelligence Identities Protection Act. Saying that Plame's position was "classified" is not a violation of the Intelligence Identities Protection Act.
Notice he didn't say, "I can't comment on that." He SPECIFICLY SAID HE WAS NOT SURE OF HER CLASSIFIED STATUS AT THE TIME.