Manifold heat cross over physics and benifits

I wonder if the heat cross-over was designed for worst-case conditions, like Alaska or Minnesota.

Yes, they try to design the vehicles to work in every condition that it may encounter. They are tested in Death Valley, Colorodo Springs, Pikes Peak, Phoenix, and throughout Texas to make sure that they perform under extreme heat. Then to Bimidji, MN and upper Michigan for the cold portion of the testing. Bimidji records the coldest temps in the US.