I think "rounded" and "radiused" are the same thing, just using different terms.

I'm on the road right now so no pics yet, but without "rounded" the butt cap can have a bit of a sharp edge on it, especially with a "commando" grip (the shape of which extends into the butt cap).

Capt pointed that out to me awhile back when I ordered a Big Bear Bowie with a commando leather handle. He was right, of course.