More vicissitudes of rank

The show: JAG
The episode: "Family Business," first aired October 8, 2002, now on Disc 1 of the Season 8 set.
What happened: Gunnery Sergeant Joe Akers (Tyler Christopher) is accused of killing his wife. He claims it was self-defense and he was the victim of spousal abuse. Harm (David James Elliott), assigned to defend Akers, is frustrated that Akers won't let his son testify. Meanwhile, Bud (Patrick Labyorteaux) almost gives up on his physical therapy because his father won't come visit him in the hospital.
What the writers neglected, again: In Season 6 I complained about a Pfc. being constantly referred to as just "Private." Now, in this episode, both Lieutenant Colonel Sarah "Mac" MacKenzie (Catherine Bell) and Harm refer to Gunnery Sergeant Akers as just "Sergeant," or worse, "the Sergeant."
I can kind of understand Harm making that mistake, and I can understand Akers not complaining: in real life, a Gunnery Sergeant wouldn't be afraid to tell an officer not to call him just "Sergeant," but given that the officer in this case is his defense attorney, whose hand he is figuratively tying behind his back by not allowing him to talk to his son, being called two ranks lower just isn't his most pressing problem. But why does Mac also make that same mistake? She's a Marine and she ought to know the Marine enlisted ranks thoroughly. Besides, even though she has not trouble with everyone calling her "Colonel," she certainly wouldn't enjoy being called just "Lieutenant."