My new cruiser bike has a twist shifter on the straight handlebar. Why is there more space on the dial between the numbers 6 & 7? The space between every other number is the same, except between the 6 & 7. I'm a little OCD.
While most shifts rely in the very position of the shifter to precisely place the derailer aligned with the cog, the last gear relies in the limiter screw in the derailer itself. So, the last gear usualy "let the cable go" a bit more than needed, so that the limiter screw handles it.
Also, in the last gear, the derailer spring is almost unloaded, so that extra release of cable helps the last shift to happen.