As I recall, the faceted look of the early stealth aircraft was said to be a practical matter. It reduced the complexity of modeling the reflections during the design process. So with additional computational complexity, they could go back to smooth surfaces in later designs.

I imagine there are similar issues with ship design. Since these things are wavelength specific, you probably have a bigger computational problem for a bigger vessel. You can't just solve for the design on a miniature and scale it up to build it.