It could be a bit of a slippery slope. I love visiting NWR locations, but there is definitely a difference from the National Parks. I'd probably have a hard time recalling all the NWR places I've enjoyed over the years.
For usanp, I'd suggest sticking to sites administered by the National Park Service and leave anything covered by the Fish & Wildlife Service out. Same goes for Forest Service roads.
You should still go, but the route doesn't belong in usanp (in my opinion).