In the specific situation of SWA feeding, say, an outhouse which was going to be TTd (hence SWA armour not be be touchable at the outhouse end), I would have thought that there would be quite a good argument for using a non-metallic gland, otherwise one would have to be careful to ensure that the body of the gland was, and remained, 'untouchable'.... Yes, you could use a nylon stuffing gland, but that would be nasty. Just use the correct gland and don't connect the gland body to earth.
Kind Regards, John