It's a drug, it effects your behaviour/mood, you must have done some weird shit on it
The liquid you drink with filtered coffee has had much more time to steep in all the caffeine from the crushed beans compared to the espresso machine where the liquid travels though the crushed beans under high pressure. This graph might also consider size, but an americano is usually a double espresso with more water so i think they are refering to the brewing method and not the size.