You obviously have the blinders on still, as you completely missed the explanation. It's in sentences 4 and 5 in my above post and i'll give the gist here again. I hope the blinders will be off this time. BDs are bound to use dual swords to activate dances, hence they get dual weapon mastery, it's only weapon they technically should use. SWS are not locked into dual swords to perform their songs therefore they do not get dual weapon mastery. Thats the weapon mastery you seem to be concerned about and microscoping to death, that is the reason. Also i was pointing out that each class has strengths the other doesnt, every counterpart is like that.