"[Name of person] is no longer one of Jehovah's Witnesses."
I can see how this could still result in charges of slander. The announcement is that the person is no longer one of Jehovah's Witnesses. The phrase "one of Jehovah's Witnesses" is not a title... it is a condition. Basically it means that one is a Witness of a deity named Jehovah.
Basically it would be the same as a preacher of one religion specifically naming a preacher of another religion and then calling him a Satanist. That is slander.
The reason they will never say one "is no longer a Jehovah's Witness" is because that will be an admission on their part of agency over the individual... something the WTS has faught tooth and nail in court so that they will not be help liable for the actions of JWs.