Look at her hair physics in this video it looks almost exactly like project diva f and x physics and the face model looks like f and x faces!
Why do you think that this is a prototype? The title even says that the video is from MikuPa, one of the live concert of Miku. As for the similarities with Project Diva titles, SEGA is known for scraping their concert data and add them into Project Diva. Another example and Looks familiar?
I know its from mikupa look at the title first but havent you looked at the similarities firs to project diva f and x
I think I mentioned this. SEGA not only makes Project Diva games. They also make animations for live concerts and other things that related to Miku and friends (e.g. few TV commercials) and they are also love to "maximize the usage of their exsiting assets". If you still have any doubt, try to search concert recordings for songs in Project Diva. There should be more examples of fully and partially reusing the animations from the concert in Project Diva games.