It's a bit of fun
What actually happened fits very well with that bit of fun narrative. Using a bunch of incorrect stuff detracts from the funness.
my example: the storm troopers didn't wear black. The SS did. But they didn't just wear black, they had runic emblems and skulls and shit. This minor detail is important because remembering details about genocide is probably a good thing.
See Mitchel and Web for a better example.