Are you perhaps on the latest alpha release version?Like, did you know that the guard power is strongly based on the kind of weapon the NPC has equipped even if that NPC is not skilled enough to use it in actual combat? The wiki says nothing about this. My Lovisa, who is completely unfit for any combat and has the guard power value of 1 (which is the base value) can get a value of 11 if I equip her with a power katana and a coil gun. Even giving her some garbage pistol and knife gets her to 5; sledgehammer (which she absolutely cannot use lol) brings her up to 6. An NPC with no weapon equipped gets a -1 penalty so it's absolutely necessary to have any sort of weapon equipped on them.
Because that's a brand spanking new feature, so it's no wonder it's not in the wiki yet.
Guard value got a rework there, and new raider attacks on the house were added, so that guard equipment matters.