In practical terms, for me, the width of the screw head skirt on a ground screw is about the same as the side wired device terminal screw head skirt. It works reasonably well on stranded and fine on solid.
Now, if I'm forced to use a standard 10-32 round head machine bolt for a ground screw, I'd argue that the skirt is so narrow that even solid wire won't reliably terminate under it.
