Everyone else in the thread understood what Ashton was asking about. It's actually you who's confused and distracting to the wilderness. You posted this:
"Residential service at the two cable 500 wire cable interface could be AB, BC or AC two-phase 240v. It depends upon how the utility classifies it."
None of that changes what split-phase is, what it looks like at the panel in his house or has anything to do with the question. And in fact most split-phase in the US is created using just ONE primary phase, with the pole transformer connected between one of the three phases and neutral, ie Wye formation. That's what you see driving down the road, one pole transformer after another here. That transformer has a center tap that then provides 240/120V split-phase to the home. That is how the utility "classifies it" and looking at it, at the panel, looking at it's electrical characteristics, it looks the same and makes no difference how exactly it was created, nor does it have any impact on the questions he asked. And it's THREE conductors, typically in one cable that provides that service.