The line about the midi-chlorians was actually added by Lucas during the making of the book in 2007. The original EU guidelines had no mention of them.
Source: http://www.starwars.com/news/so-what-the-heck-are-midi-chlorians
(scroll about half-way down to the note by Rinzler. He says, “Please note: While we were preparing the text for The Making of Star Wars, Lucas added a note to this passage about midi-chlorians, bringing his original words in line with his later thoughts and the events of the prequel trilogy.”)This is the original, historically accurate EU guideline about the Force:
“The Force is really a way of seeing; it’s a way of being with life. It really has nothing to do with weapons. The Force gives you the power to have extra-sensory perception and to be able to see things and hear things, read minds and levitate things. It is said that certain creatures are born with a higher awareness of the Force than humans. Their brains are different. The Force is a perception of the reality that exists around us. You have to come to learn it. It’s not something you just get. It takes many, many years…Anyone who studied and worked hard could learn it. But you would have to do it on your own.”
Strange, considering how Rinzler points out at the beginning of the chapter that none of the things he’s quoting is part of an “official continuity” and merely represents Lucas’ thoughts on the matte in 1977. So why let him alter it?
Now I’m starting to wonder what else may have been altered, like f.ex. Threepio’s backstory of being “totally reassembled by a young boy working for a junk dealer”.
Anyway, I’ve fixed the original post to mention this.