On another site they often incorrectly refer to the 1-phase system as a 2-phase. It comes from the confusion that it has two wires. But a true 2-phase system would still need at least three wires and often uses four. True 2-phase systems are very rare and basically don't exist in vehicle charging systems.
When you only have 2 wires, the current carried by the wires can only ever have a single net value at any given moment, so it can only ever have one phase.
In order to have two phases, you need to have two different currents at the same time. This requires more than two wires.
In a single closed loop circuit, the current is the same single value everywhere on that loop. To have two distinct currents, you need two loops, which requires at least three wires (or three connections) coming from the power source.
2-phase systems in industrial applications are often used when one phase has a different purpose than the other phase, and because of that, the power or voltage requirements may be different so the physical wire requirements will be different. As such they will use 4 wires instead of 3. Or it could be that the two phases need to be electrically isolated from each other. None of this would apply to a simple power generation implementation like we have on the Kz.
The 550 FSM refers to it as single-phase. I use 1-phase as shorthand.
The rotors ( aka flywheels) have 6 north and 6 south poles, so it can work with a 12-pole 1-phase stator or 18-pole 3-phase stator since 6 divides nicely into 12 or 18.
It's been a long time since I had the north and south poles confirmed on a rotor that came on a 1-phase system, so I'm going on memory and previous posts I made. The only puzzling thing is: why do the rotors from 1-phase systems have a different part number from those of a 3-phase. It could just be some improvement in the magnets or some other minor change, but I never got to the bottom of that yet. At any rate, several users confirmed the same rotor works with both types of stators.