That was something that entered my mind when I saw "OW 40". But I have only seen this in a synthetic. I expect that the use of VI additives in synthetic oil is a different ball game due to the superior behavior of synthetic oil at high temperature.
I have absolutely no data to back up this statement, it's only a hunch.
From a practical viewpoint, I think that there would be very few people in need of such a weight spread. I suppose if your drive included a run across the desert at 110 degree F ambient, followed by climbing the mountains into -20 degree F ambient, there would be a need for such an oil. I would expect this to be a need for much less than 1% of drivers in the world.
I just would not see where this would be a need. If you're in Alaska, use 0W 30, if you're on the equator, use 20W 40. With a synthetic, 10W 30 would probably work on the equator quite nicely.