I am not sure this genre truly exists outside of Allmusic's categorization scheme (same with "Modern Creative", "Early Creative" etc.) This article cites the Allmusic page about the genre, in addition to two other sources that I am not sure make a strong case that it's an actual genre:
I do not believe the Daniel Wichert piece qualifies as a reliable source for this article. The text is in German, but that isn't my biggest concern. I understand a little German, enough to to ascertain that the title page indicates this was written for a school (presumably as an assignment), and that the document itself is hosted within an online collection of student papers.
As for the second source, the book Jazz: a Regional Exploration, Scott Yanow does mention the term "free funk", however he also writes for Allmusic and so I still question whether this genre is (notably) used outside of Allmusic and/or its contributors.
