I’m afraid that’s a little misleading, Balanced Drive has 2 amps in series with the load, moving in opposite directions
By symmetry the (usually inaccessible) midpoint of the load doesn’t move and can logically considered to be grounded for figuring load currents, this makes it easy to see that the Load Impedance is Halved as seen by each amplifier in Balanced Drive
With 2 amps in series with the load there is 2x the amp output impedance – so you get 2x the influence of the Amplifier Output Impedance on the sound
The Voltage swing of each output amp side is halved for the same power and even order distortion products that are common to both amplifiers can cancel
By symmetry the (usually inaccessible) midpoint of the load doesn’t move and can logically considered to be grounded for figuring load currents, this makes it easy to see that the Load Impedance is Halved as seen by each amplifier in Balanced Drive
With 2 amps in series with the load there is 2x the amp output impedance – so you get 2x the influence of the Amplifier Output Impedance on the sound
The Voltage swing of each output amp side is halved for the same power and even order distortion products that are common to both amplifiers can cancel