Super Boo's Japanese name is officially "Majin Boo (Evil)." Super Boo is a term used as a throwaway in the dub when Gotenks-Boo/Gohan-Boo describes himself, plus M12 came out after Vegetto had already appeared in the manga, and even in development it was written after Toriyama had already decided to fuse Goku and Vegeta together which was way way way after Super Boo first appeared. Nothing indicates Super Janemba is meant to parallel Super Boo. If anything he might more likely have inspired Kid Boo since both are pure evil creatures that do not have the intelligence to speak and push SSJ3 Goku around.