I've collected ~100M Super Jackpots, but still apparently hadn't cracked the Super Jackpot champ. Does it possibly only take into account the raw, unmultiplied value of the SJP? That is, disregarding playfield multipliers and the stacked SJP multiplier? (edit: confirmed, it is the base, 1x SJP; you don't even necessarily need to collect it, it seems)
But then again, I'd take a lot of the "x champ" scores with several grains of salt. I've had Terror Dog champs that exceeded my entire score.