Except that differing wheel sizes give different driving characteristics. Larger wheel diameter > lower profile tyre > better handling due to less side wall movement, but worse ride due to the stiffer side wall.
Some drivers might think it just cosmetic, but it's not.
Just a poor analogy for this discussion. Let's stay on topic eh ?
Is that fraction of a millimeter really that important when all the other factors are taken into consideration ? tolerances for manufacture, drilling, gluing etc. I can't see that myself.
You missed the point too. The idea is to have a bush kit, maybe as many as 36 individual simple and cheap components, but that's all you ever need for any combination of tube and component as long as designers can accept the slight compromise of working to fixed 1mm increments of diameter of a part.
