On a few occasions where I had a NuVinci hub that were undergeared, I tried to see if, when twisting the gear selector toward the lowest range, whether the hub bottomed out before I finished twisting the selector, or does the gearing keep going lower until I finished twisting the selector. Although the gearing was so low that it all felt like I was pedaling while the chain fell off, I kind of felt that the last 20% of the twist did not do anything. The whole cable attachment area is covered in that plastic sheath, so I can't peek in to see if there was a slack in the cable, although the cables operate in a push/pull design, there shouldn't be any slack.

That doesn't mean if the cable is properly attached so the bike will shift into overdrive, that the shifter's shifting range allows the hub to shift into the lowest gearing possible.