TX,

Point taken.
But then connecting the ends of the chain together, and picking random segments to wrap around each of the cog and the chainring, would influence the tension on each unsupported side. The machining of the teeth on the cog and chainring now affect the tension of those segments, which will change as the crank is turned.

I think you have a better chance of eliminating a "cyclic" tightening/loosening of the chain if you pick a different set of teeth to wrap. The gear ratio is going to affect the "skid patch", ie the number of unique combos of teeth engaged at both the cog and chainring.

Runout is easy to check. It would seem to be difficult to make an "out of round" ring or cog, unless they are simply stamped.