Actually that does make sense. The balance port also senses the actual voltage of the battery and not just what the charger is putting out. In other words, there is a voltage drop across the charging lead from the charger to the battery. Without the balance port the charger uses the voltage learned on the charge leads, which will be higher during a charge than the actual battery. Because of that it will get to constant voltage mode faster. As the current goes down there will be less and less voltage drop so the battery still charges up fine, but takes longer.