Note the penultimate processing step (previous campaign within timeout), which has a significant impact on the direct channel. Consider a user who discovers your site via organic search, then returns via direct a week later. Both sessions would be attributed to organic search. In fact, campaign data persists for up to six months by default. The key point here is that Google Analytics is already trying to minimize the impact of direct traffic for you.
The term “organic traffic” is used for referring to the visitors that land on your website as a result of unpaid (“organic”) search results. Organic traffic is the opposite of paid traffic, which defines the visits generated by paid ads. Visitors who are considered organic find your website after using a search engine like Google or Bing, so they are not “referred” by any other website.