Rattus,
Think of two cars that start from a stop at the same time. The first one is accelerating faster than the second one. They are both moving forward, they are both accelerating. But, if you are sitting in the faster car looking back at the other one, you will see that the car behind you is dropping further behind. Now, for some reason, if you consider yourself to be travelling at "zero" miles per hour (after all, you are 'sitting,' right?) the car that is behind you actually appears to be travelling backwards.
There is a very fundamental difference between single and three phase systems. The three phase systems have a time displacement between phases. Ergo, the word "phase." Single phase systems only have a "single phase."
Mathematical subscripts are simply a means to describe something in the real world. The real world is not governed by the math, it is the other way around.
I think we are all really saying the same thing, but we have different contexts. What is actually happening inside the transformer is one context. What you see on a scope with the leads hooked up in a certain configuration is something entirely different.