I get what you're saying, amps are pulled, not pushed. But you should consider ohms law. Hand to foot, with a dry hand, typically is 400ohms. You can pull a lot of amps through 400 ohms if the voltage is high enough
The focus here is the 30-750 volt range with tens of amps, with a secondary mention of neighborhood power lines. For injury purposes, we can treat all of these as having unlimited amps available. By the time there's enough kilowatts going through your body to notice the curve shifting, we're well past the point of wondering whether or not you die.
My point is that the number of amps you can get from the circuit is irrelevant, it's "more than enough" and that's all you need to know beyond the voltage and the exact way the human is being exposed.
