It is a good idea, @how, but social coding movement is scoped differently than that. And precisely so that a seamless liaison with SocialHub is there. SocialHub has this implementation directory, already.
Social coding movement is more about the applied research and related tools ecosystem (but as autonomous initiatives under its umbrella) of collaboration processes and best practices for Sustainable open social systems / software / services.
So e.g. @dansup’s Pixelfed would be out of scope to be directly under the movement’s umbrella (i.e. have forum space etc.), while the various developer tools and the respectable platforms are candidates to be direct initiatives under its (already very vast) potential scope.
Furthermore creating these subcategories is not how the movement operates. Doing this work would involve community management, and the movement isn’t a community. It is self-servicing itself as the instance of a hedonic commons-based peer production system… it must grow itself based on proactive participation, and otherwise it just sits and waits.
Yet there may be an autonomous initiative along your idea. I have thoughts there myself, except more longer-term ones. They start with the protosocial fellowship proposal, and the mutual recognition of our liaison, as per the polls in Wellbeing, participation, processes and policies
For both of these I can say the interest is lukewarm, and then I am being positive. This is no wonder, as things do not work like that without commons janitors stepping up to volunteer. Which is rare.
The movement is timeless, slow, starts tiny, is humble… and may grow exponentially. But that is not up to me. I am just a one man crazy horse. 
