I have used a dual trace scope and looked at 3 phase waves that are 120 degrees out of phase and two waves from a transformer with center tap that are 180 degrees out.
Doesn't matter how you cut it, when waves are 120 out of phase, you want to call it 3 phase. When 2 waves are 180 out of phase, you want to call it single phase. Do you see the irony?
However, there are motors working on single phase that use a run capacitor on the start windings and you call them poly-phase motors.
Guess you don't want to call a poly-phase motor a 2 phase motor. Poly sounds better!
No need to explain, I understand phase angles, how 3 phase generators are made.
BTW, most alternators are actually 3 phase, some heavy duty are 4 phase.