Clear documentation must also provide a context for the readers in order to explain why they are reading the text. If not, your documentation is probably less effective than it should be. Writing clear documentation is not easy. You can't rely solely on the Fog Index to determine readability. Have a colleague or a professional writer review your text thoroughly for simplicity and accuracy.
Nobody likes to read through fog.
Make sure your readers don't have to. By the way, this article's Fog Index, not counting the passage from the technical article, is 12.3. All rights reserved. No part of this document may be reproduced in any form without the expressed written consent of the author. Inc. All Rights Reserved.