This change was made to remove the restrictions in NWN about which creature/class can wield which weapon and too allow weapons like bastard swords and spears to be used either single handed or two handed. This is all in accordance with PNP. Unfortunately the animations are all single handed now because the NWN engine thinks that every weapon is a single handed weapon; the spear looking particulairly sill as it is swung like an axe.

IIRC there was some discussion about making this change optional for people who didn't want to lose the two handed animations but the changes were too extensive to make this practical.