What happen if the Supreme Kais were removed from Good Buu's body?
Remember that Fat Buu was removed from the Fusion/Super Buu. Both of the original Kais had long since been fully absorbed/consumed, and Fat Buu was the only thing left. Once Goku removed Fat Buu (also Supreme and Ultimate Kais), then Kid Buu (original) is what we are left with. If they had still been inside of Super Buu, then Goku/Vegetta would have seen them near Fat Buu.