It appears that charger does use the main power leads as part of the balancing setup. On the typical three wire 2s balancing port two of the wires are connected same as the main leads. Only drawback I can see would be a possible slight voltage error due to different wire resistance.

The reason balancing is not required with nicads & nimh is because those cells don’t normally burst into fire if overcharged a little. (explode maybe, but not burst into flames lol)

It would help them though, reduce heat build up. Spintec makes a charger with 6 separate floating ground charge channels that accomplishes the same thing.

http://spintec.nl/ICC.shtml