It seems a bit more complicated that that as Eddie's reacted to more than just "bombs" and "marshmallows". Marshmallows could be excluded if Keela didn't alert, but Eddie could still have been reacting to... the innocent presence of garden fertilizer or whatever components go into making them. Or he might have accurately detected a bomb.
Garden fertilizer ! If the garden fertilizer smelt cadaver, nobody would buy it !
Eddie wasn't trained to identify, in a compound, the eventual presence of some components of cadaver scent. He was trained to recognize
the combination of all components of cadaver scent. . This is why synthesized cadaverine wouldn't do.
Why are you trying to denigrate the dog, Carana, it wasn't proved the cadaver scent came from Madeleine body, so relax !
And besides, Eddie knew when he was at work, i.e when he had to find, or not, the scent he had been trained to recognize, and only that scent.