Fair enough.
One more comment. Ultimate Combat p.130 states regarding grapple weapons:
Quote:
While you grapple the target with a grappling weapon, you can only move or damage the creature on your turn. You are still considered grappled, though you do not have to be adjacent to the creature to continue the grapple. If you move far enough away to be out of the weapon's reach, you end the grapple with that action.
The above seems pretty clear to me that you're actually using the weapon in the grapple maneuver. Hence, a grapple weapon's bonuses should apply to grapple maneuvers.
So this seems similar to a trip weapon's bonuses applying to drag/reposition maneuvers.