You're probably right. Again, I don't think the Treadwrights are a good choice for those wanting to air down really low. However, other 4X4 enthusiasts have done this and witnessed no adverse effects. I wouldn't do it though.
Perhaps you misunderstood my comparison. I wasn't questioning that your old Dunlops were a better snow tire than your present M/T's. I was taking issue with the fact that you used that comparison to determine that the severe winter rating was the cause for such a disparity. In the world of statistics, that wouldn't stand. In your second post, you refer to your friends vehicles that also feel more stable in the snow. While this does provide a little more information, it still doesn't provide sufficient evidence to make your claim. One would have to have a good sample of non-severe winter rated tires as well as a good sample of sever winter rated tires along with a consistent surface to test each tire on. After quantitatively measuring each tire's performance, one could run a regression analysis by identifying the severe weather rating as the independent variable. Should the severe weather rating have a meaningful effect on each tire's performance then, one could say that such tires are better in the snow.
By analyzing two sets of tires on one slope at different times, your comparison is flawed and incomplete. While everything may have seemed the same, it is impossible to know the condition of the layers under the surface of the snow. There could have been a sheet of ice for the one instance, and soft ground for the other.
The truth is that no one probably cares to perform such a study so unless someone does, let's just say that M/T's may not be the best snow tire around, and that severe winter rating tires may be. I'll also add my 2 cents by saying that for the entire Salt Lake City winter, I haven't had any slipping, stopping or other traction issues with my tires, whatsoever.