If the behavior "makes sense" to the player, we have succeeded.
It's worth noting that what makes sense to the player is something we can (to a certain extent) teach the player during the game.
Imagine a few scenarios:
You're surrounded by enemies, and they all suddenly take cover without warning just before a thrown grenade explodes.
You stealthily take out a guard in a far-off location. As you're looting the corpse, 15 other enemies show up.
Both of those could feel very unfair to the player -- the AI is cheating!
Now imagine the same scenarios, but imagine they are telegraphed to the player.
One of the enemies shout "Fire in the hole!" right before the group of enemies take cover.
You hear radio chatter on the corpse's walkie-talkie, which sounds more and more distressed, before the rescue party shows up.
The AI didn't need to change, but now the game feels a lot more clever, because we've been more explicit in telling the player something which makes the actions make sense to them.
Of course, this isn't always wanted or beneficial, but it's definitely worth keeping in mind.