The string length in relation to the nut and bridge does have an effect on the instrument. I can't remember the physics involved, but the reason a MM Stinkray has the G tuner where it does was that Fender figured out that dead spots on a P bass were a result of the longer G string. Moving it changed the tension with it in tune, and got rid of the dead spot. Somebody will know what it involves. So - from all I recall - a compensator tailpiece does effect the instrument, as does reversing the headstock. Maybe minor, but I don't think it is a myth. But then again I don't recall all the details either.