The current version of Carv does not have the ability to detect how far apart your feet are, so it cannot directly measure a wide or narrow stance.
However Carv does measure the full 3D orientation of each of your feet. For example, it knows when one of your legs is at a more aggressive angulation than the other, so can detect problems such as A-framing. It can also detect how parallel your feet are, so it knows for example if you have a tendency to snow-plough at the initiation of each turn.
And using the pressure sensors, Carv can detect your weight distribution between skis around the turn. So it knows, for example, if you're not putting enough weight on your outside ski in the middle and later stages of the turn.