There'll be more angle variation in the hands, than from the rods moving, when using the SM. The SM is still essentially a 'freehand' device, albeit with an easier means to 'eyeball' a correct sharpening angle by holding the blade perpendicular to the horizontal base. When used properly on a steady support with light pressure, the rods should settle to the outside limit of their 'wiggle' room in the base, and shouldn't move anyway, even if a bit loose. If there were enough slop to produce an obvious & visible asymmetry in the edge angle (comparing one side to the other) when viewed statically, then there'd be some cause for concern.
A lot of V-crock sharpeners, like the SM, will be a bit loose in fit for the rods. The other systems with (imprecisely) drilled wooden bases are often much worse, introducing other problems like asymmetry, with the 'V' of the rods tilted to one side and not perpendicular to the base. In this respect, the molded base for the SM is definitely better.
David
