Hi Jcook0113,
Well, you can do that with the f/stop selector because the iris itself is continual, ie, it opens and closes smoothly, not by discrete clicks.
Shutter speeds, however, are controlled by a spring mechanism with discrete settings; if you set it between 2 speeds, it will give you 1 or the other speed, and you can't predict which one, ie if you set the selector between 1/250 and 1/500 seconds, you won't get a speed between the two like 1/375, you'll just get one or the other marked shutter speeds.
Terry