Fiction vs Nonfiction

I've seen this bit of advice several times: When you're writing nonfiction, you should make up some details, or embellish them, to make your writing more vibrant. It's the story, not the facts that matter.

 I can see where they're coming from. I guess that's different than making sure to do good research before you write about a topic. You stretch the facts to make the writing more powerful. But I have to admit, these kinds of advice make me question what I read. How much of it is true?

But so far I try to keep my fiction and nonfiction separate. I want my nonfiction to truly reflect the world around me. I don't think I need to make things up. The world is fascinating enough, as long as I can do it justice in my words. 

(Howl's Moving Castle)

Plus I get plenty of opportunity to make stuff up in my fantasy stories.