I totally forgot about the sidemarkers - nor can I recall, but aren't the sidemarkers similar to our turns, aka, constant on when lows are on.

I tried a ad-hoc test with a relay with the turn as trigger. Default *parking lights on*-*constant 12V active*, it will still causing the switchback halos to freak out. I think the simple elimination of the hot 12V and just hot 12V when turns will alleviate the issue and now that you bring it up (spazzed moment), if I disable parking lights, I still have sidemarkers.