My point is this:
If your rim is centered by the hub AND by the lugs the two processes will work against each other unless VERY tight tolerences are held during manufacture.
If you were to purchase a true hub centric rim (assuming that our hub was designed for it, which I doubt) and installed it using lug nuts that are designed to also center the rim. The conical nuts would try to adjust what the hub has already aligned. One of two things will happen (prolly #2)
1. The hub or the centerbore of the rim will deform to allow the rim to center somewhere between where the hub had it & where the lugs want to put it. Congratulations, you've just violated the hub centric design that you wanted so badly.
2. The lug nuts won't tighten properly and will eventually vibrate loose. Nobody wins in that situation.
Like I said in an earlier post, in all likelihood our factory rims are lug centric & just happen to have a fairly tight fit to the hub but are not hub centric.