To me it means you shouldn't turn the busbars over any more. Then it doesn't matter.
I like the feel of a regular nut on a flat washer. Personal preference.
I know you weren't asking me. I'm sure Campin has thoughts since you were asking him.
It didn’t matter then I read ArthurEld’s comments Lol. And I prefer to torque a flat surface in this case. If something vibrates loose, I’ll use low-strength locktite.