I don’t mean to split hairs, but the WP article you linked has the following sentence:
“Petraeus, in the end, pleaded guilty last year to a misdemeanor charge of mishandling classified material.”
So, it appears that the Justice Department never presented the *felony* charge to a grand jury, but instead charged Petraeus with a *misdemeanor* to which he plead guilty.
I agree. I’m not a lawyer either ... thank God. From that POV he was charged.