Since they are continuous controls, I don't see how you would get discrete frequencies. Any increase in resolution from an identical frequency sweep range would have to come from a pot with a greater amount of rotation. I doubt that the pots are that different. There might also be a difference in taper of the pot, but I'd be surprised if they used one taper for one set of electronics and another in a different set. It wouldn't make much design sense or economic sense in terms of having to stock different types of pots. However, I'm perfectly happy to be proven wrong!