Sorry for the vague title, this is because I am not entirely sure of the spoiler policy here. I'm making this post because I have not found a thread addressing the fact that
Hellknight Hill spoiler:
Calmont has a +1 shortbow listed in his items, but his bonus to attack with it is the same as it is with his nonmagical dagger. The math seems straightforward, level 3 + 2 for trained proficiency + 4 for Dex, which is +9. The +1 shortbow should therefore be at a +10 to hit, unless I misunderstood something about the workings of the game.
Can anyone explain to me if I'm wrong?
Stats/item bonuses don't quite work the same way for NPCs as they do for PCs.
If a creature loses its weapon, it might draw another
weapon or use an unarmed attack. If it uses a Strike it
doesn’t have listed in its stat block, find a Strike entry
for the creature that most closely matches the substitute,
reduce the attack modifier by 2, and use the damage
dice for the new Strike. If the creature needs to make an
unarmed attack and doesn’t have one listed in its stat
block, it uses the statistics for a fist (Core Rulebook 280).
If the creature loses a weapon with a weapon potency
rune, you usually should reduce the attack modifier by 2
plus the bonus granted by the weapon’s potency rune for
the new weapon. For example, if the creature is Disarmed
of its +1 mace, then you would reduce the attack modifier
by 3 instead of 2 for the new Strike.
The above Bestiary entry seems to contradict your commentary(still, you may be right, I'm just not sure of where to look for information to affirm it.