<< When one is seasoned by sparring and/or combat; they always keep the front leg slightly bent; one who spends all of their time on forms/Katas only; does not. When you advance, your training prevents this. >>
I can speak only for Iaido where basically all activity is in the form of kata. A front leg not slightly bent would be the object of a considerable lecture from Sensei.
That's because sword arts get their stances right!
My Karate teacher says that the most simple sword fighting stance is the best stance I tend to agree with him but learning the movement is quite hard at first..