This is a bit off topic, but think of what happens to maintenance guy's example if you use standard 120 single phase and a scope instead of a volt meter.
I've never tried it, but I assume that If you use the neutral/ground as 0 and the look at the two hots, you will see two sine waves seperated by a phase shift of 180 degrees, so you have two phase current (but not real two phase).
But if you use one of the hots as 0, and look at the neutral and the other hot, you will see 2 sine waves in phase 1 with twice the amplitude of the other, so you only have single phase current.
I guess it just depends on your point of view.
