This would be a leak of classified info as well

From Newsweek:

In May, the State Department's intelligence unit had prepared a secret memorandum about the provenance of Wilson's journey and its classified results—including the curious fact that Wilson's wife, a CIA agent then working on weapons of mass destruction issues, had been involved in planning the mission, and had even suggested that her husband undertake it.

If Rove, or anyone else, told any journalists, or any other source who didn't have the appropriate security clearances and need to know, that they thought or heard or read that Plame was involved in planning the mission to Niger, that too is classified information that they leaked. That's yet another layer to the possible criminal activity involved in this case.