That's been my experience Mike, many were like the 520 (ballast and by pass circuit) others not why I added that disclaimer (moreso on 520). I guess if he has 4 wires (2 on each side) it must be wired like the later 520's. I've also seen different switches at vendor booths, the 20 series needs the MAG or GRND terminal for this purpose and that switch can also be used as a kill switch for a Mag ignition tractor as it provides a ground when OFF.
Were getting pretty detailed on this one but Ive seen this question raised before.
Fun chattin at ya