I think I have an explanation for the weird Bladesharp text.
The Bladesharp text appears almost verbatim in RQ3, but in RQ3, Dullblade merely subtracts damage, without reducing hit chance. Hence, it's a perfectly sensible comment in RQ3 - it clarifies that first Bladesharp adds both hit chance and damage, but then Dullblade merely removes damage rather than the other possible interpretation, that it negates the whole Bladesharp spell in its entirety. (RQ3 Magic Book pp 19-20.)
When the Bladesharp text is applied unchanged to RQG while Dullblade has been (sensibly, in my mind - symmetry is good) changed to now reduce hit chance as well, it stops making sense.