This is a catchy (and graphic) aphorism, but it's false. The quote merely describes inspiration for writing, not the labor of writing itself.
Anybody can have an idea. For particularly creative people, inspiration strikes from anywhere: out of thin air, from a dream, levitating off your refrigerator or a TV show or a broken curtain rod. Granted, good ideas are more difficult to create, but ideas themselves are a dime a dozen.
Artistry and lots of editing separate great writing from mere puddles of inspiration. Every first draft should be fed to a large fire, and every third draft still has a ways to go. Hemingway's quote--if he was the one to say it at all--ignores the writers' craft entirely, which, irony aside, is insulting. It makes good writing look easy.
My novella is currently 5000 words. It started off as a two-page outline which nobody would call good writing. That title belongs to the prose and the emotions and the struggling description.