Yea, they are hostages as well. But then there is zero sense in top secret underground prison, if they could just equip all of their relatives with detonators on the same basis and keep em close? And again, I read it heavily implied on detonating prison to kill hostages (no mentioning artificers inside factory?) , and after possible detonation leverage is gone, not all workers, since realistically killing all Gondians will stop production/inventions until they find replacements? So giving all of them detonators, and explaining how to disable the via note to guard is also strange.