What other rotating register file architectures are you aware of? It’s a bit of an esoteric topic, and as such, hints are generally needed for research.
As for why the Mill isn’t mentioned, what is there to mention? Academia exists in the hubristic double-thought that it knows all things worth knowing (while simultaneously knowing that most of those things came from outside). As far as I know, there are no academic papers concerning the Mill, as the Mill is a commercial project through-and-through: it is the kind of project that papers will be written about in retrospect (if a product is ever launched). As such, there is nothing to really cite, except some videos of talks given at a university that were high-level and abstract in order to protect IP. That really is the nature of the project, and the nature of academia.
Right now, the Mill is a rumor, possibly another piece of industry vaporware, and this STRAIGHT is an academic play toy.