I think you’re mostly right. I don’t think Libby would have been charged if he had not, allegedly, lied to the investigation. (I take your reference to “testified” to include both Scooter’s FBI interviews and his grand jury testimony.)
I have to qualify with “mostly” because of your insertion of “I didn’t think her identity was classified …”.
In the perjury charge in Count Five, the prosecutor is recorded as having asked Libby about an assertion by Libby that he “did not understand the information about Wilson’s wife to have been classified” when he spoke with reporters. Libby is said to have replied, in pertinent part: “I didn’t know it was true and I wanted [the reporters] to understand that.”
The indictment strongly implies – but I don’t believe it says explicitly anyplace – that Libby knew Plame’s employment status with the CIA was classified. However, the above exchange is alleged to be perjury. That only makes sense to me if the government is claiming Libby absolutely knew about the classified nature of Plame’s employment status, and that when he said he didn’t, he was lying.
I’ll have more to say about Count Five in a moment.