The separate ground leads makes it easier for me to understand how that arrangement can work. By sensing condition using both of the battery terminals, all the external variable like voltage drop across jumpers is eliminated. In addition, using pulsed charging the voltage and current states over short periods of time probably enables the charger to more accurately determine status as opposed to a simple voltage measurement.I also have difficulty fully understanding the concept as well. Each charge lead has a separate ground to the negative terminal on the battery itself. A total of eight leads. My thought is if you treat the battery as a load on the charger it will have resistance, some degree of capacitance and some degree of inductance. These new chargers are simply not fixed DC output. I believe they do a pulse DC which could be thought of as pseudo AC but not sinusoidal. Given that, there is a big difference between two parallel resistors and parallel capacitors or coils. I have taken a number of electrical engineering courses up to circuit design, but that was years ago when we drew on paper and used a slide rule to calculate circuit parameters. Things have come a long way.
It's interesting technology.