If one must have a certain mind to see things in a certain way, you can be sure you're dealing with a healthy dose of perspectivism. And that's really the central argument of Wallace Stevens's "The Snow Man." In Stevens's world, the reality outside of the realities our individual imaginations create is, well, boring, and that very idea is the hinge on which this poem swings.
This poem has one big hole in its logic: snow is snow, no matter what kind of mind you've got.
This poem isn't perspectivist at all. It's nihilist, and in the end, Stevens proves that nothing exists. At all.