You have always said that speakers with a crossover should never be wires in series, yet here you are, saying that a dual voice coil speaker can be wired in that way. That's wrong.
You don't seem to understand the intent of a dual voice coil speaker.
These ARE for allowing both channels to play from one spot. It's done everywhere and amplifiers don't fail because of it. Millions of these have been installed with L and R wiring and that's how they're supposed to be wired. It's not mono, it's stereo from a coaxial speaker without separation. These are made for places where two speakers can't be installed.
The input of the autoformers buffers the speaker impedance from harming the amplifier, although it's impossible to know if that will be effective without knowing what will be used as an amplifier in this system. Some volume controls even have extra taps to allow maintaining the impedance when up to four speakers are used on one control. These have been available for over 30 years and they work.