With what you are talking about the points of two alignment bars intersecting and touching as if everything was OK, would need both rings to be off exactly the same amount and in the same direction... almost impossible, thus is why you get one point slightly above/below or to one side... does it hurt to use both way, no... fact is best scenario would be to check using both way's. But point to point is easier to spot unless (both rings are off exactly the same amount and in the same direction).
