Is this saying that Musashi only uses the same five stance system as Iori while Berserker? If so I'm glad they're differentiating her Berserker and Saber skillsets, up to now she looked exactly the same.
It’s essentially saying Saber Musashi sticks only to traditional Niten Ichiryuu because she is a serious swordswoman who takes swording seriously therefore would NEVER use shit techniques on purpose. Berserker Musashi, on the other hand, is obviously doing the good Niten stuff too, but she can also copy Iori’s five forms because it’s funny.