While I agree in general, a good quality burr grinder is surprisingly consistent. I'm not sure you could reliably get distinct results one notch apart, but at a given notch you will have a very narrow spread in grain sizes and a couple notches apart they will be visually distinct. James Hoffman has some videos comparing several cheap and expensive grinders, including looking closely at the grain size, and you can see the difference clearly.
Surprisingly consistent when measured using coffee that is ground to hundreds of microns is not an indicator about consistency at the few microns level. Use high quality calipers on the burrs, you’ll be shocked how much variance you see run to run at one adjustment, never mind what happens when you move the dial. Micron marks on grinders are pure marketing.
Even if your coffee grinder is in a room temperature-controlled to within 1 degree, the heat output of the motor could easily cause more than 5 microns of thermal expansion.
But obviously, if the coffee tastes good to you, then that's a coffee making success regardless of how precisely you're grinding things.