I have heard of such a thing as "hard fantasy", but it's a very small niche and seems to be running on crossover appeal to hard SF fans as much as anything else. As best I can tell, readers of fantasy valuing high Openness have instead migrated to the New Weird subgenre (exemplified by China Miéville, Mike Mignola, etc.); epic and heroic fantasy aren't as hidebound as they were before the mid-1990s, but they're still a highly stereotyped body of writing.

(I think using The Iron Dream as an example is a little disingenuous, though; it's essentially an essay in novel form about the parallels between fascist mythology and heroic fantasy of the pulp tradition. Using it to demonstrate the same seems to assume its conclusion.)