I donīt think that this is possible. The tail is a lot closer to the main gear, so the plane would have to drift a LOT more than if it had been the nose wheel (what we also donīt know for sure). So the 7° mentioned before for the nose wheel would be some 30°-40° for the tail (just a wild guess), which would bring the main gear tracks closer together.
I tend to think that the straight line stems from the nose wheel, what is not completely consistent with that however is, that a drift of the airframe should bring the main wheel tracks closer together (which might be lost in the angle of the photo).