Line honing crank journals

How's a tensioner going to "fix" a possible timing issue? If the distance between the two gears is too close with a standard chain, the chain is too long. I don't care if the chain is pulled taut by the tensioner or by natural forces, the chain is still too long which throws the timing off a little. Obviously a shorter chain is the only real answer, or you can start playing around with the gearsets that have offset keys/keyways.