If you can tell the difference in a stock photo between a half inch then your eyes are far more calibrated than mine.
Many wheels companies simply add or subtract material from the hub mounting surface to change offset with the same width wheel. A change of 8mm in the offset would hardly necessitate an entirely new mold. This holds even more true for companies with smaller profit margins, aka cheaper wheel companies.
How dare you doubt my supervision!!
...but yeah, you might be right. Then again would a wider wheel even be a factor? Isn't offset just distance from hub to outside of the wheel. Added with would only change the distance from the hub to the inside of the wheel. They might limit amounts of molds but i'm pretty sure they've gotta have at least two molds. The one in that pic and the one on my car.