Well, in their defense, they did include the disclaimer that, aside from the automotive firsts, they were restricting the cars to post WWII because "there was a lot of seriously weird shit created before then."
Of course, that doesn't explain everything, but at least they put a pre-war section down at the bottom that accounted for some of your notations.
Largest pre-war Straight-4 - 21.5 L (21495 cc) - 1912 Benz 82/200 (Wow. Just freaking wow.)
Largest pre-war Straight-6 - 21.1 L (21112 cc) - 1905 Panhard et Levassor 50 CV
Largest pre-war Straight-8 - 12.8 L (12763 cc/778 in³) - 1929 Bugatti Royale