Comey said she didn’t lie to the FBI.
Duh. They didn’t question her until that Saturday, and even then she wasn’t under oath.
Under oath doesn’t make a difference in talking to the FBI (or a lot of other government agencies). False statements are illegal regardless.
Martha Stewart and Scooter Libby were convicted of making false statements to the FBI.
Comey couldn’t admit she lied. It would open her to prosecution. So he exonerated her of e-mail offenses and claimed she didn’t lie about any of it when questioned by the FBI.