I've noticed that ogres behave strangely with wall gratings.
This ogre is more than content to stare at me through the grate rather than to walk around it and smash me up.
Not so, because they turn to face me. they want to attack me because they can see me, but they can't attack through the grating so they just stare at me instead.
Gratings are doors for the ogre ai, and doors can't be sidestepped like that in the grimrock dungeon so the ai was never tweaked with this case in mind. It's a "feature"