I have always assumed an offset fletch was just that....offset from the center of the arrow but still parallel.
No, I don' t believe that the offset is parrellel with the shaft.
I don' t think it would be possible to fletch an arrow the way you have it in your offset picture PA. That is unless there are specially make fletches. I would imagine, that the bottom of the fletch would have to have some sort of incline running lengthwise in order for the vane or feather to sit the way you have it in your picture.