GHB = Get Home Bag.
I don't use them because I like them with frames, and they don't ride as well in my TJ (Jeep) the way my frameless Recon Ruck does.
If I "got home" and had to get out, I'd transition to the large ALICE, most likely. Or at least the medium, even though the Recon Ruck is just slightly higher capacity. Maybe mount the Recon Ruck on a frame (it is kind-of an updated ALICE, with the addition of MOLLE webbing). Because then the frames would be very much an asset.
I guess the GHB is almost the opposite of a BOB. My thought is most likely the scenario is gonna involve me being at work when things go down, and wanting to get home to the family to determine the next steps. So, one step at a time, stepping up/out in bags as I go: (1) GHB; (2)BOB; (3) INCH.