Mike,
On the few 12g sxs guns I've taken the time to look at, the barrels were each straight, but converging. I don't recall the amount off hand now. But the number is substantial. Measuring the outside across both muzzles and then back a foot will give you an idea of the convergence. The barrels do indeed "cross point of aim", but the theory is that the recoil causes the gun to rotate and align the barrel with the point of aim (POA)as the payload exits the barrel.