The factory wheels are lug/stud centric. They also use the hub bore to roughly align the wheel during install, but it's the lug taper that does most of the precision locating.
The taper on the lug nuts may center the wheel, but the studs were designed to handle the lateral forces that pull the wheel away from the mounting. They were not designed for the shear stress of tire to road impacts or the weight of the car. Remember, you only have 4 bolts on these wheels.
That's correct, and the lugs do not see shear force unless there's been a lug-nut failure. That's why there's a hub face. That friction holds the wheel to the hub. The car only has 4 bolts because the car isn't heavy enough to necessitate more clamping force to create more wheel/hub friction. This is the same rationale how multi-piece wheels work and the wide-5 hub on the VW Beetle works; sufficient friction through clamping force.
Hub centers exits for a reason. Car and wheel manufactures see a need for hub centers. If it was ok not to be hub centric, all wheels would be made with 75 mm center holes and you could use them on any vehicle.
Yes you're right on all counts, but not for the reason you're likely implying. They exist to make the factory's job as easy as possible. The hub bore does not hold any weight of the car in normal operation. If it did, you couldn't use flimsy plastic hub-centering rings. Most aftermarket wheels use a large generic bore [e.g. 73mm is common], and space it down with nylon or ABS rings per application.
