Tangent: why is it four ‘A’s? Why not just “A6”? Is there a technical reason?
Christian Huitema is listed as an author on both AAAA and A6 RFCs, so maybe they know why the AAAA identifier was originally chosen instead of A6. Unfortunately, Google doesn't provide any "AAAA" hits for their blog at https://huitema.wordpress.com/.