Kurt-
No doubt that quality control can make a difference out of the box. But it is not simply the rings that generate the need for lapping; bases, the rifle platform itself and the location of base screw holes each affect the final alignment of the rings every bit as much as the rings themselves.
Even in your case, we can't say that lapping wasn't required until
after you lapped, yes? Therefore.....lapping was required!
Regards-
Rich