Overcharging

MSD igntion does not care if the ballast resistor is there or not. So its not a given than an MSD = no ballast resistor. You could have left it in, as I did.
In fact that's what the original instruction suggest - they also used to provide jumpers so in an emergency it was easy to use the oem system.

When starting a car, battery voltage should drop! If it doesn't go below 10 V, the battery is pretty good.

With the increasing voltage with rpm to 16 V - if it stablizes at 16 V by say 1250 rpm, then yes, its a resistance problem.

The regulator will work properly for the information it is given.
So to answer your question; Yes it matters where the regulator 'reads' voltage.

When there is excessive resistance in the lines leading to the regulator, it will see a lower voltage than the alternator is producing at.
The voltage drop through the resistance will vary with current. See post #33 if that doesn't make sense.

See the previous page about how a negative controlling regulator works.