As the co-creator of Scribe I am more than happy to address your question.
First, Scribe is not a keyword density checking tool. It is designed to help writers in creating and structuring their content so search engines can better "understand" and index the content.
Second, Scribe contains a number of other features including keyword research/analysis, internal link organization and intelligent ways to connect your content with other sites through online relationship building tools. For a complete overview please go to http://scribecontent.com/demo/ for a video overview.
As to your specific point.
While density does not matter, frequency does. In information retrieval, term frequency is a very important part of most publish search algorithms used at conferences like TReC, etc. To see its importance, there are several excellent mathematical examples at http://www.miislita.com/ . Please note that Dr Garcia, who publishes at this site and was a consultant to us on Scribe v4, is the one that penned the epic "Keyword Density of Non sense" post that disputed the role of density as a ranking factor.
A key component of "understanding" content is both in the analysis of term frequency and term placement. While density calculations, when done properly, do provide some insight as to relative usage; the reality is that most all search systems review term frequency and weight it with other factors in order to determine the probability that a specific document is related to the query.
I think that Moosa H makes a good point in that you do want to write for humans first. Scribe helps you improve your writing to make it easier for search engines to understand what you are writing about.
Samer, thank you for your question and I hope my response provides some clarification to your question.
