Why do SXS barrel bore diamiters vary?

[SXS OHIO]

I have been looking at several American SXS guns and notice that bore diameter can very by 10K from each other? If gun is factory original why would that happen? or is this not normal practice and avoid guns with wide variations. Say a 16ga....left is .655 and right is .668 Would this be indication of hone job? Should it be a deal braker if all else is in spec? I would think that a proper bore job would be the same for both tubes or are the barrels bored prior to jointing them together and luck of the draw? thanks all SXS ohio My question is...did the barrels leave the factory bored the same in each tube? Like .662 and .662 ???/ Thanks all SXS ohio....(-: