Sadly, here I got this: http://nwn.wikia.com/wiki/Weapon_finesse
"The finessable weapon list includes all standard small and tiny melee weapons, plus the rapier (which is medium). "
"Even though the feat description says 'light weapons', this should not be confused with light weapons in the context of dual-wielding. The finessable weapons are exactly the ones listed above, regardless of the size of the weapon and the size of the wielder (with the noted exception that two-handed weapons cannot be finessed). "
So I think maybe it's "shouldn't" in fact & I'd better give this up