I don't totally follow everything you're saying here, but what I was trying to explain before was that if multiple ground connections are tied to a single point (i.e. the ground paths from multiple circuits all converging at one location), and that common ground point is cut, then current seeking ground that'* coming down one wire will double back through the others to find it. This can result in two devices running at half-power in series; e.g. headlamps at half-brightness along with whatever else is tied to the same (broken) ground connection.

High-low beam headlamps (i.e. the outboard or upper lamp on an older four-light setup) can do this all by themselves if their ground contact isn't connected to anything: power to the low-beam filament goes through it and out the other side, then doubles back through the high-beam filament if the headlamp'* own ground connection is broken, and finds a good ground somewhere else on the high-beam circuit. That'* why that headlamp goes to half-brightness if it loses its ground, rather than going out altogether.

AAH.. that makes sense.. got ya thanx tech info junkie hee hee...