I’m not sure that is the case. It’s clearly violative of the law and it’s a crime to disclose info that was obtained under color of law but obtained thru means not authorized by the act. I would think unmasking is in that category.
When it comes to committing a crime, the question boils down to citing the statute, and correlating the facts with the elements of the crime. The crime that precedes leaking (and this crime can be by a different person), one must conduct electronic surveillance. So, under your view, unmasking is engaging in electronic surveillance.
I sure hope you don't get the impression that I am defending political unmasking. It's banana republic level stuff. IF we had a decent society, Rice would be shunned out of it for political unmasking, and here pretextual justification would be rejected out of hand. But we don;t have a decent socitey. Half of it, and nearly all of the press, finds nothing untoward in politically-motivated unmasking, when it cuts in their favor.