Alas, that one is intended.
The intent was that you could turn off an extra barehanded attack if your offhand was empty, mostly for two handed weapon use, honestly, but if you're using no weapons at all, in the normal engine, the actor would still make a barehanded attack, so his main hand should always be considered armed, even if he has a weapon in his offhand.
Changing that in particular would be difficult because the plugin was not designed with that in mind. Attacks always come from the main hand first, the only exception being if the offhand is locked during a skill. To change it permanently would be much more involved than the change I did to make the offhand empty attack not trigger.
~Ramza