Psychic Lobotomy and Confusion Immunity

[Dracos]

Got surprised pretty hard on Daikara where just everything seemed to ignore most of the mental effects I had going on, and just was wondering if I was reading something right.

So Giants have Confuse Immunity, which seems to also be Sleep immunity. Not obvious, but I can follow it now that I get it.

Psychic Lobotomy though I'm not sure on. It says it does Mental Damage, reduces cunning, and has a chance to confuse. When used on giants, it seems to do...nothing. I get that confusion is blocked, but I thought it'd at least still be a damage dealer. Is it expected that it doesn't do damage either if an enemy is Confusion immune?

Actually, given that the Dreaming Eye gives +100 Sleep Immunity (which shows up as Sleep Immunity)...is Confusion Immunity supposed to give Sleep Immunity? It definitely seemed to (40+ difference in mindpower versus mind save repeatedly failing to sleep giants around daikara 1 and 2).

Not quite sure whether bug, or just not understanding it.

[GlassGo]

Giants react just like any non-living creature, like xorns, crystals, bone giants.