Yes, at the most basic, the thread is about his extension, and not a SketchUp issue, so belongs in the Extensions category. Sometimes, this kind of post might be in the Developers category, if the poster only wished to solicit testing by other devs.
In your title you used the term "Gray Area". Sometimes that is just what it is. A few moments ago, I was about to move a post, and decided not to, as I couldn't absolutely agree with myself that moving the post would benefit finding it easier later. (Which is mainly the reason for separating posts into categories.)