1A amperage is a feature of saltwater eels, ones that produce electricity at much lower voltages, like 10-80V. This is a natural adaptation allowing them to maximize power output in a relatively highly conductive environment.
The freshwater eels, the ones producing 600-800V, are only able to output about 0,1A, because that’s just how power works.
1A at 600V would be almost a guaranteed instakill for a human.