Great post! I have one issue with it however. You imply that when a wheel or spacer is hubcentric then the protruding part of the hub shares some of the load. This is generally not the case once the wheel nuts are properly tightened. The majority of the load from the wheel to the suspension/knuckle is carried through static friction between the hub face and the wheel mounting face and it is the clamping load of the properly torqued nuts that make sure that this friction is sufficient.

In order for the protruding hub area to carry any load with a hubcentric wheel placed on it the fit between the centrebore of the wheel and the outer diameter of the protrusion on the hub would have to be extremely tight, bordering on a press fit. This is not the case.

Wheels being hubcentric primarily aids in getting the wheel centred when mounting so this is particularly important when using spacers as there is greater potential for mounting the wheels off centre which can cause havoc. I don't believe that it is essential that aftermarket wheels be made hubcentric with the use of hubcentric rings however.