What's wrong with Katanas?
Nothing, but having Daedric Japanese weapons is a little..well.."Who the hell would do that?". The fact the Japanese inspired weapons were all over the place was one thing, but as super rare as Daedric is supposed to be, you've somehow got Daedric varieties, too.
To think of something that would be similarly out of place (but doesn't exist) think "Daedric Crossbow". See what I mean?