I may just get rid of that, but whatever was the case with NWN1 should still be the case now... I think maybe you got certain bonuses on one hand but not the other if you offhanded it (detailed discussion found elsewhere on the interwebz), I won't belabor it because it's all hardcoded.
I was working on a Trip script per SRD, but it looks like NWN1 just gave whip wielders Disarm for free. This isn't the thread for that but we'll find a happy medium.
Cum eos testibus arripuisses, eorum corda mentesque sequentur