I truly hope that they are categorized differently because if not, they would be subject to 250.104[C] and 250.104[D],2 which would mean a bonding conductor brought back to the service entrance and could also allow metal stud walls to be used as a grounding electrode for a transformer, as Reno pointed out earlier, since there could be a separately derived system serving one area of a building.
The thin gauge stamped steel studs walls are held together with short self-tapping sheet metal screws and could be required to carry a tremendous amount of fault current under the wrong circumstances. This is not very safe or adequate IMO.
Metal studs are no different than screw-set couplings with respect to impedance and quality of bonding, yet the latter are considering adequate for grounding...
If I was writing the code book, I would require ground wires to be run with
every circuit so that none of this other metal is primary fault grounding path... but I would still required it to be bonded to ground. I like the florida code, too, that allows them to be bonded to the largest circuit they're liable to be energized with. If only 20A runs are near that wall, #12 is fine for bonding, etc.
If properly run (with grommets or strain relief couplings, etc), steel studs are no more dangerous to romex that metal panel enclosures or handy boxes. Just because somebody "might" get lazy with it and ignore the rules is no reason to ban it.
